Influenza

Absolute humidity and temperature are the most important environmental drivers of global influenza, despite differences in outbreak patterns between tropical and temperate countries, according to a new analysis by U.S.-based researchers.

Using convergent cross-mapping and an empirical dynamic modeling approach on data collected by the World Health Organization, investigators led by George Sugihara, PhD, of the Scripps Institution of Oceanography at the University of California, San Diego, confirmed a hypothetical U-shaped relationship between influenza outbreaks and absolute humidity. At low latitudes in the tropics, absolute humidity has a positive effect, increasing the likelihood of influenza as humidity rises but at higher latitudes in temperate countries, absolute humidity has a negative effect, making influenza more likely when absolute humidity is low.

While absolute humidity was the most important factor in the likelihood of influenza outbreaks, the U-shaped relationship was dictated by average temperature. An average temperature below 70 °F had little effect on the negative relationship between absolute humidity and influenza at that range of temperatures, but if the temperature was between 75 °F and 85 °F, the effect was positive. Above 85 °F, aerosol transmission of influenza is blocked, the investigators noted.

“Augmented with further laboratory testing, these population-level results could help set the stage for public health initiatives such as placing humidifiers in schools and hospitals during cold, dry, temperate winter, and in the tropics, perhaps using dehumidifiers or air conditioners set above 75 °F to dry air in public buildings,” Dr. Sugihara and his colleagues wrote.

Find the full study in Proceedings of the National Academy of Sciences of the United States of America (doi: 10.1073/pnas.1607747113).
 

[email protected]

Absolute humidity and temperature are the most important environmental drivers of global influenza, despite differences in outbreak patterns between tropical and temperate countries, according to a new analysis by U.S.-based researchers.

Using convergent cross-mapping and an empirical dynamic modeling approach on data collected by the World Health Organization, investigators led by George Sugihara, PhD, of the Scripps Institution of Oceanography at the University of California, San Diego, confirmed a hypothetical U-shaped relationship between influenza outbreaks and absolute humidity. At low latitudes in the tropics, absolute humidity has a positive effect, increasing the likelihood of influenza as humidity rises but at higher latitudes in temperate countries, absolute humidity has a negative effect, making influenza more likely when absolute humidity is low.

While absolute humidity was the most important factor in the likelihood of influenza outbreaks, the U-shaped relationship was dictated by average temperature. An average temperature below 70 °F had little effect on the negative relationship between absolute humidity and influenza at that range of temperatures, but if the temperature was between 75 °F and 85 °F, the effect was positive. Above 85 °F, aerosol transmission of influenza is blocked, the investigators noted.

“Augmented with further laboratory testing, these population-level results could help set the stage for public health initiatives such as placing humidifiers in schools and hospitals during cold, dry, temperate winter, and in the tropics, perhaps using dehumidifiers or air conditioners set above 75 °F to dry air in public buildings,” Dr. Sugihara and his colleagues wrote.

Find the full study in Proceedings of the National Academy of Sciences of the United States of America (doi: 10.1073/pnas.1607747113).
 

[email protected]

Absolute humidity and temperature are the most important environmental drivers of global influenza, despite differences in outbreak patterns between tropical and temperate countries, according to a new analysis by U.S.-based researchers.

Using convergent cross-mapping and an empirical dynamic modeling approach on data collected by the World Health Organization, investigators led by George Sugihara, PhD, of the Scripps Institution of Oceanography at the University of California, San Diego, confirmed a hypothetical U-shaped relationship between influenza outbreaks and absolute humidity. At low latitudes in the tropics, absolute humidity has a positive effect, increasing the likelihood of influenza as humidity rises but at higher latitudes in temperate countries, absolute humidity has a negative effect, making influenza more likely when absolute humidity is low.

While absolute humidity was the most important factor in the likelihood of influenza outbreaks, the U-shaped relationship was dictated by average temperature. An average temperature below 70 °F had little effect on the negative relationship between absolute humidity and influenza at that range of temperatures, but if the temperature was between 75 °F and 85 °F, the effect was positive. Above 85 °F, aerosol transmission of influenza is blocked, the investigators noted.

“Augmented with further laboratory testing, these population-level results could help set the stage for public health initiatives such as placing humidifiers in schools and hospitals during cold, dry, temperate winter, and in the tropics, perhaps using dehumidifiers or air conditioners set above 75 °F to dry air in public buildings,” Dr. Sugihara and his colleagues wrote.

Find the full study in Proceedings of the National Academy of Sciences of the United States of America (doi: 10.1073/pnas.1607747113).
 

[email protected]

The 2014-2015 influenza vaccines offered little protection against the predominant influenza A/H3N2 virus, but were effective against influenza B, according to the vaccine effectiveness estimates provided by the U.S. Flu Vaccine Effectiveness Network.

Preferential use of the live attenuated influenza vaccine (LAIV) among young children, a recommendation previously published by the Advisory Committee on Immunization Practices, was not supported.

During the 2014-2015 influenza season, a total of 9,710 patients seeking outpatient medical treatment for acute respiratory infection with cough were enrolled into the U.S. Flu Vaccine Effectiveness study, reported Richard Zimmerman, MD, of the University of Pittsburgh, and his colleagues (Clin Infect Dis. 2016 Oct 4. doi: 10.1093/cid/ciw635).

Of these, 9,311 participants had complete data, and 7,078 (76%) tested negative for influenza. A total of 1,840 participants tested positive for influenza A – 99% of these cases were strain A/H3N2 – and 395 participants tested positive for influenza B.

Of the 4,360 vaccinated participants with known vaccine type, 39.7% received standard dose trivalent, 1.6% received high dose trivalent, 46.8% received standard dose quadrivalent, and 11.9% received quadrivalent live-attenuated vaccines.

©luiscar/Thinkstockphotos

The study was supported by the Centers for Disease Control and Prevention and the National Institutes of Health. Dr. Zimmerman and four other investigators reported receiving research funding from several pharmaceutical companies.

[email protected]

On Twitter @jessnicolecraig

The 2014-2015 influenza vaccines offered little protection against the predominant influenza A/H3N2 virus, but were effective against influenza B, according to the vaccine effectiveness estimates provided by the U.S. Flu Vaccine Effectiveness Network.

Preferential use of the live attenuated influenza vaccine (LAIV) among young children, a recommendation previously published by the Advisory Committee on Immunization Practices, was not supported.

During the 2014-2015 influenza season, a total of 9,710 patients seeking outpatient medical treatment for acute respiratory infection with cough were enrolled into the U.S. Flu Vaccine Effectiveness study, reported Richard Zimmerman, MD, of the University of Pittsburgh, and his colleagues (Clin Infect Dis. 2016 Oct 4. doi: 10.1093/cid/ciw635).

Of these, 9,311 participants had complete data, and 7,078 (76%) tested negative for influenza. A total of 1,840 participants tested positive for influenza A – 99% of these cases were strain A/H3N2 – and 395 participants tested positive for influenza B.

Of the 4,360 vaccinated participants with known vaccine type, 39.7% received standard dose trivalent, 1.6% received high dose trivalent, 46.8% received standard dose quadrivalent, and 11.9% received quadrivalent live-attenuated vaccines.

©luiscar/Thinkstockphotos

The study was supported by the Centers for Disease Control and Prevention and the National Institutes of Health. Dr. Zimmerman and four other investigators reported receiving research funding from several pharmaceutical companies.

[email protected]

On Twitter @jessnicolecraig

The 2014-2015 influenza vaccines offered little protection against the predominant influenza A/H3N2 virus, but were effective against influenza B, according to the vaccine effectiveness estimates provided by the U.S. Flu Vaccine Effectiveness Network.

Preferential use of the live attenuated influenza vaccine (LAIV) among young children, a recommendation previously published by the Advisory Committee on Immunization Practices, was not supported.

During the 2014-2015 influenza season, a total of 9,710 patients seeking outpatient medical treatment for acute respiratory infection with cough were enrolled into the U.S. Flu Vaccine Effectiveness study, reported Richard Zimmerman, MD, of the University of Pittsburgh, and his colleagues (Clin Infect Dis. 2016 Oct 4. doi: 10.1093/cid/ciw635).

Of these, 9,311 participants had complete data, and 7,078 (76%) tested negative for influenza. A total of 1,840 participants tested positive for influenza A – 99% of these cases were strain A/H3N2 – and 395 participants tested positive for influenza B.

Of the 4,360 vaccinated participants with known vaccine type, 39.7% received standard dose trivalent, 1.6% received high dose trivalent, 46.8% received standard dose quadrivalent, and 11.9% received quadrivalent live-attenuated vaccines.

©luiscar/Thinkstockphotos

The study was supported by the Centers for Disease Control and Prevention and the National Institutes of Health. Dr. Zimmerman and four other investigators reported receiving research funding from several pharmaceutical companies.

[email protected]

On Twitter @jessnicolecraig

Procalcitonin can help predict which patients with community-acquired pneumonia may require intubation for respiratory failure during a hospital admission.

Compared to those with undetectable levels, patients with a procalcitonin of 5 ng/mL were three times more likely to require invasive respiratory support, and those with a 10 ng/mL level were five times more likely, reported Wesley Self, MD, and his colleagues (Chest. 2016;150[4]:819-28. doi: 10.1016/j.chest.2016.04.010).

While predictive accuracy isn’t good enough to merit use of procalcitonin as a stand-alone test, adding it to existing clinical management tools “is likely to improve identification of patients needing intensive care,” wrote Dr. Self of Vanderbilt University, Nashville, and his colleagues. “An elevated procalcitonin level may help identify these patients without overt clinical signs of impending respiratory failure or shock but who would benefit from early [intensive care unit] admission.”

The team examined serum procalcitonin as a biomarker in a subgroup of patients included in the Etiology of Pneumonia in the Community (EPIC) study of adults hospitalized with community-acquire pneumonia. The primary outcome was the need for invasive respiratory and/or vasopressor support (IRVS) within 72 hours.

Secondarily, they looked at whether adding procalcitonin boosted the performance of accepted pneumonia risk scores, including the American Thoracic Society minor criteria (ATS).

The cohort comprised 1,770 patients with a median age of 57 years. Of these, 115 (6.5%) needed IRVS within 72 hours of admission. Almost 16% were admitted directly into an intensive care unit; almost 7% experienced a delayed transfer from a medical unit into an ICU. The in-hospital mortality was about 2%.

Most (1,642) had an ATS score of less than 3; among these, about 5% needed IRVS. The remainder had a score of 3 or higher; about 30% required IRVS. All had procalcitonin levels pulled at admission. The levels were significantly higher among patients who required IRVS than those who didn’t (1.43 ng/mL vs. 0.14 ng/mL).

A multivariate analysis found that procalcitonin was strongly associated with the risk of IRVS. In patients with undetectable levels, the risk was 4%. At 5-10 ng/mL, the overall risk of IRVS was about 14%. Every 1-ng/mL increase in this range boosted the risk of IRVS by 1%-2%.

Adding the measurement of procalcitonin to traditional pneumonia severity risk scores significantly improved the patients’ performance. When stratified by ATS minor criteria, the risk of IRVS was 4.7% among low-risk patients. That decreased to 2.4% with the addition of undetectable procalcitonin, and increased to 12% with the addition of a 10 ng/mL level.

Conversely, without considering procalcitonin, ATS high-risk patients had almost a 30% risk of IRVS. Among these high-risk patients, IRVS risk dropped to 13% with undetectable procalcitonin and increased to 36% with high procalcitonin.

Adding the biomarker level to the ATS system improved its ability to correctly classify patients, the team said. “Using at least 3 ATS minor criteria alone to indicate high risk, 77 (4.4%) of the 1,770 total patients were misclassified as low-risk and experienced IRVS. Including procalcitonin of at least 0.83 ng/ml in addition … as a high-risk indicator reduced the number of patients with IRVS misclassified as low risk to 44 (2.5%). Adding procalcitonin of at least 0.83 ng/mL as a high-risk indicator resulted in 370 additional patients being classified as high risk, with 33 correctly classified as having IRVS.”

Dr. Self reported financial relationships with multiple pharmaceutical companies.

[email protected]

On Twitter @Alz_Gal

Procalcitonin can help predict which patients with community-acquired pneumonia may require intubation for respiratory failure during a hospital admission.

Compared to those with undetectable levels, patients with a procalcitonin of 5 ng/mL were three times more likely to require invasive respiratory support, and those with a 10 ng/mL level were five times more likely, reported Wesley Self, MD, and his colleagues (Chest. 2016;150[4]:819-28. doi: 10.1016/j.chest.2016.04.010).

While predictive accuracy isn’t good enough to merit use of procalcitonin as a stand-alone test, adding it to existing clinical management tools “is likely to improve identification of patients needing intensive care,” wrote Dr. Self of Vanderbilt University, Nashville, and his colleagues. “An elevated procalcitonin level may help identify these patients without overt clinical signs of impending respiratory failure or shock but who would benefit from early [intensive care unit] admission.”

The team examined serum procalcitonin as a biomarker in a subgroup of patients included in the Etiology of Pneumonia in the Community (EPIC) study of adults hospitalized with community-acquire pneumonia. The primary outcome was the need for invasive respiratory and/or vasopressor support (IRVS) within 72 hours.

Secondarily, they looked at whether adding procalcitonin boosted the performance of accepted pneumonia risk scores, including the American Thoracic Society minor criteria (ATS).

The cohort comprised 1,770 patients with a median age of 57 years. Of these, 115 (6.5%) needed IRVS within 72 hours of admission. Almost 16% were admitted directly into an intensive care unit; almost 7% experienced a delayed transfer from a medical unit into an ICU. The in-hospital mortality was about 2%.

Most (1,642) had an ATS score of less than 3; among these, about 5% needed IRVS. The remainder had a score of 3 or higher; about 30% required IRVS. All had procalcitonin levels pulled at admission. The levels were significantly higher among patients who required IRVS than those who didn’t (1.43 ng/mL vs. 0.14 ng/mL).

A multivariate analysis found that procalcitonin was strongly associated with the risk of IRVS. In patients with undetectable levels, the risk was 4%. At 5-10 ng/mL, the overall risk of IRVS was about 14%. Every 1-ng/mL increase in this range boosted the risk of IRVS by 1%-2%.

Adding the measurement of procalcitonin to traditional pneumonia severity risk scores significantly improved the patients’ performance. When stratified by ATS minor criteria, the risk of IRVS was 4.7% among low-risk patients. That decreased to 2.4% with the addition of undetectable procalcitonin, and increased to 12% with the addition of a 10 ng/mL level.

Conversely, without considering procalcitonin, ATS high-risk patients had almost a 30% risk of IRVS. Among these high-risk patients, IRVS risk dropped to 13% with undetectable procalcitonin and increased to 36% with high procalcitonin.

Adding the biomarker level to the ATS system improved its ability to correctly classify patients, the team said. “Using at least 3 ATS minor criteria alone to indicate high risk, 77 (4.4%) of the 1,770 total patients were misclassified as low-risk and experienced IRVS. Including procalcitonin of at least 0.83 ng/ml in addition … as a high-risk indicator reduced the number of patients with IRVS misclassified as low risk to 44 (2.5%). Adding procalcitonin of at least 0.83 ng/mL as a high-risk indicator resulted in 370 additional patients being classified as high risk, with 33 correctly classified as having IRVS.”

Dr. Self reported financial relationships with multiple pharmaceutical companies.

[email protected]

On Twitter @Alz_Gal

Procalcitonin can help predict which patients with community-acquired pneumonia may require intubation for respiratory failure during a hospital admission.

Compared to those with undetectable levels, patients with a procalcitonin of 5 ng/mL were three times more likely to require invasive respiratory support, and those with a 10 ng/mL level were five times more likely, reported Wesley Self, MD, and his colleagues (Chest. 2016;150[4]:819-28. doi: 10.1016/j.chest.2016.04.010).

While predictive accuracy isn’t good enough to merit use of procalcitonin as a stand-alone test, adding it to existing clinical management tools “is likely to improve identification of patients needing intensive care,” wrote Dr. Self of Vanderbilt University, Nashville, and his colleagues. “An elevated procalcitonin level may help identify these patients without overt clinical signs of impending respiratory failure or shock but who would benefit from early [intensive care unit] admission.”

The team examined serum procalcitonin as a biomarker in a subgroup of patients included in the Etiology of Pneumonia in the Community (EPIC) study of adults hospitalized with community-acquire pneumonia. The primary outcome was the need for invasive respiratory and/or vasopressor support (IRVS) within 72 hours.

Secondarily, they looked at whether adding procalcitonin boosted the performance of accepted pneumonia risk scores, including the American Thoracic Society minor criteria (ATS).

The cohort comprised 1,770 patients with a median age of 57 years. Of these, 115 (6.5%) needed IRVS within 72 hours of admission. Almost 16% were admitted directly into an intensive care unit; almost 7% experienced a delayed transfer from a medical unit into an ICU. The in-hospital mortality was about 2%.

Most (1,642) had an ATS score of less than 3; among these, about 5% needed IRVS. The remainder had a score of 3 or higher; about 30% required IRVS. All had procalcitonin levels pulled at admission. The levels were significantly higher among patients who required IRVS than those who didn’t (1.43 ng/mL vs. 0.14 ng/mL).

A multivariate analysis found that procalcitonin was strongly associated with the risk of IRVS. In patients with undetectable levels, the risk was 4%. At 5-10 ng/mL, the overall risk of IRVS was about 14%. Every 1-ng/mL increase in this range boosted the risk of IRVS by 1%-2%.

Adding the measurement of procalcitonin to traditional pneumonia severity risk scores significantly improved the patients’ performance. When stratified by ATS minor criteria, the risk of IRVS was 4.7% among low-risk patients. That decreased to 2.4% with the addition of undetectable procalcitonin, and increased to 12% with the addition of a 10 ng/mL level.

Conversely, without considering procalcitonin, ATS high-risk patients had almost a 30% risk of IRVS. Among these high-risk patients, IRVS risk dropped to 13% with undetectable procalcitonin and increased to 36% with high procalcitonin.

Adding the biomarker level to the ATS system improved its ability to correctly classify patients, the team said. “Using at least 3 ATS minor criteria alone to indicate high risk, 77 (4.4%) of the 1,770 total patients were misclassified as low-risk and experienced IRVS. Including procalcitonin of at least 0.83 ng/ml in addition … as a high-risk indicator reduced the number of patients with IRVS misclassified as low risk to 44 (2.5%). Adding procalcitonin of at least 0.83 ng/mL as a high-risk indicator resulted in 370 additional patients being classified as high risk, with 33 correctly classified as having IRVS.”

Dr. Self reported financial relationships with multiple pharmaceutical companies.

[email protected]

On Twitter @Alz_Gal

Individuals with type 2 diabetes should receive the seasonal influenza vaccines annually, as doing so significantly mitigates their chances of being hospitalized for – or dying from – cardiovascular complications such as stroke, heart failure, and myocardial infarction.

“Studies assessing influenza vaccine effectiveness in people with diabetes are scarce and have shown inconclusive results,” wrote Eszter P. Vamos, MD, PhD, of Imperial College London and her coauthors in a study published in the Canadian Medical Association Journal. “None of the previous studies adjusted for residual confounding, and most of them reported composite endpoints such as admission to hospital for any cause.”

lisafx/istockphoto.com

[email protected]

Individuals with type 2 diabetes should receive the seasonal influenza vaccines annually, as doing so significantly mitigates their chances of being hospitalized for – or dying from – cardiovascular complications such as stroke, heart failure, and myocardial infarction.

“Studies assessing influenza vaccine effectiveness in people with diabetes are scarce and have shown inconclusive results,” wrote Eszter P. Vamos, MD, PhD, of Imperial College London and her coauthors in a study published in the Canadian Medical Association Journal. “None of the previous studies adjusted for residual confounding, and most of them reported composite endpoints such as admission to hospital for any cause.”

lisafx/istockphoto.com

[email protected]

Individuals with type 2 diabetes should receive the seasonal influenza vaccines annually, as doing so significantly mitigates their chances of being hospitalized for – or dying from – cardiovascular complications such as stroke, heart failure, and myocardial infarction.

“Studies assessing influenza vaccine effectiveness in people with diabetes are scarce and have shown inconclusive results,” wrote Eszter P. Vamos, MD, PhD, of Imperial College London and her coauthors in a study published in the Canadian Medical Association Journal. “None of the previous studies adjusted for residual confounding, and most of them reported composite endpoints such as admission to hospital for any cause.”

lisafx/istockphoto.com

[email protected]

Children treated with complementary and alternative medicine (CAM) therapies were significantly less likely to receive the annual influenza vaccine than those who didn’t use alternative medicine, based on data from 9,000 children aged 4-17 years in the Child Complementary and Alternative Medicine File of the 2012 National Health Interview Survey.

“CAM has been implicated as lending support to antivaccine/vaccine-hesitant viewpoints via criticism of vaccination, public health, and conventional medicine from adults using CAM, as well as from CAM practitioners and practitioners-in-training,” wrote William K. Bleser, Ph.D., and his colleagues at Pennsylvania State University, University Park.

CAP53/iStockphoto.com

Children treated with complementary and alternative medicine (CAM) therapies were significantly less likely to receive the annual influenza vaccine than those who didn’t use alternative medicine, based on data from 9,000 children aged 4-17 years in the Child Complementary and Alternative Medicine File of the 2012 National Health Interview Survey.

“CAM has been implicated as lending support to antivaccine/vaccine-hesitant viewpoints via criticism of vaccination, public health, and conventional medicine from adults using CAM, as well as from CAM practitioners and practitioners-in-training,” wrote William K. Bleser, Ph.D., and his colleagues at Pennsylvania State University, University Park.

CAP53/iStockphoto.com

Children treated with complementary and alternative medicine (CAM) therapies were significantly less likely to receive the annual influenza vaccine than those who didn’t use alternative medicine, based on data from 9,000 children aged 4-17 years in the Child Complementary and Alternative Medicine File of the 2012 National Health Interview Survey.

“CAM has been implicated as lending support to antivaccine/vaccine-hesitant viewpoints via criticism of vaccination, public health, and conventional medicine from adults using CAM, as well as from CAM practitioners and practitioners-in-training,” wrote William K. Bleser, Ph.D., and his colleagues at Pennsylvania State University, University Park.

CAP53/iStockphoto.com

Treatment of patients admitted to the hospital with an upper respiratory infection is often complicated by the lack of diagnostics. Even in cases where a patient has a confirmed case of influenza, there is still the possibility that they may have, or become infected by, a secondary bacterial infection. This leads clinicians to treat patients empirically with antibiotics, which can result in unnecessary antibiotic use among patients without a bacterial infection.

Though antibiotics can be a lifesaving drug, their use is not without risks. Estimates suggest that 20% of patients taking common antibiotics experience some side effect. While most side effects are not life-threatening gastrointestinal effects, other nonnegligible side effects include anaphylactic shock, drug‐induced liver injury, increases in the risk of retinal detachment, serious arrhythmias, and superinfection with resistant bacteria. Antibiotics can also lead to secondary infections, such as Clostridium difficile.

Yet, despite these risks, there has been limited research on the percentage of patients with influenza who actually have a bacterial coinfection. A recent systematic review and meta-analysis conducted by my colleagues at Johns Hopkins University and the Center for Disease Dynamics, Economics & Policy examined the frequency of bacterial coinfection among hospitalized patients with influenza and identified the most common infecting bacterial species.

The findings, published in the journal Influenza and Other Respiratory Viruses, found that in the majority of studies, between 11% and 35% of patients with confirmed influenza had a bacterial coinfection. The most common coinfecting bacteria were found to be Streptococcus pneumoniae and Staphylococcus aureus. Combined, S. pneumoniae and S. aureus accounted for more than 60% of the identified coinfecting bacteria; however, many other bacterial species were found to cause infections as well.

The results suggest that while bacterial infection is common in influenza patients, only about a quarter of patients are likely to be infected. However, the studies were widely heterogeneous, both in patient makeup and results. Analyses of age, setting, enrollment year, study type, study size, and bacterial collection methods did not reveal a source for the heterogeneity in results. Thus, additional factors, such as patient comorbidities or prior antibiotic use, which could not be systematically assessed, may affect the likelihood of coinfection.

Given that the symptoms of influenza and bacterial infection often overlap, correctly diagnosing bacterial coinfection without a laboratory culture can present a challenge. This diagnostic uncertainty leads to significant overuse of antibiotics in patients with influenza alone. Most influenza cases will never result in serious bacterial infections (particularly in nonhospitalized patients), and thus a lot of antibiotic use is unnecessary. As mentioned earlier, unnecessary antibiotic use poses a nonnegligible risk to patients, but it also contributes significantly to rising rates of antibiotic resistance, a major public health issue.

The results from this study highlight that the majority of patients hospitalized with influenza are unlikely to be coinfected with a bacterial pathogen. Thus, it is important for clinicians to appropriately treat patients with antiviral drugs, and ensure that bacterial testing is done when presumptively starting patients on antibiotics. Based on the microbiology results, antibiotics can be stopped if no pathogen is identified or altered to be more appropriate depending on the pathogen found.

Although the findings of this study suggest we need a more thorough analysis of the issue, the results should still aid clinicians by improving their understanding of the likelihood of bacterial coinfection in hospitalized patients with influenza, and thus help them balance the need to minimize patient risks as well as the individual and societal risks of nonessential antibiotic use.

Eili Klein, PhD, is assistant professor in the department of emergency medicine at Johns Hopkins Medicine, Baltimore.

Treatment of patients admitted to the hospital with an upper respiratory infection is often complicated by the lack of diagnostics. Even in cases where a patient has a confirmed case of influenza, there is still the possibility that they may have, or become infected by, a secondary bacterial infection. This leads clinicians to treat patients empirically with antibiotics, which can result in unnecessary antibiotic use among patients without a bacterial infection.

Though antibiotics can be a lifesaving drug, their use is not without risks. Estimates suggest that 20% of patients taking common antibiotics experience some side effect. While most side effects are not life-threatening gastrointestinal effects, other nonnegligible side effects include anaphylactic shock, drug‐induced liver injury, increases in the risk of retinal detachment, serious arrhythmias, and superinfection with resistant bacteria. Antibiotics can also lead to secondary infections, such as Clostridium difficile.

Yet, despite these risks, there has been limited research on the percentage of patients with influenza who actually have a bacterial coinfection. A recent systematic review and meta-analysis conducted by my colleagues at Johns Hopkins University and the Center for Disease Dynamics, Economics & Policy examined the frequency of bacterial coinfection among hospitalized patients with influenza and identified the most common infecting bacterial species.

The findings, published in the journal Influenza and Other Respiratory Viruses, found that in the majority of studies, between 11% and 35% of patients with confirmed influenza had a bacterial coinfection. The most common coinfecting bacteria were found to be Streptococcus pneumoniae and Staphylococcus aureus. Combined, S. pneumoniae and S. aureus accounted for more than 60% of the identified coinfecting bacteria; however, many other bacterial species were found to cause infections as well.

The results suggest that while bacterial infection is common in influenza patients, only about a quarter of patients are likely to be infected. However, the studies were widely heterogeneous, both in patient makeup and results. Analyses of age, setting, enrollment year, study type, study size, and bacterial collection methods did not reveal a source for the heterogeneity in results. Thus, additional factors, such as patient comorbidities or prior antibiotic use, which could not be systematically assessed, may affect the likelihood of coinfection.

Given that the symptoms of influenza and bacterial infection often overlap, correctly diagnosing bacterial coinfection without a laboratory culture can present a challenge. This diagnostic uncertainty leads to significant overuse of antibiotics in patients with influenza alone. Most influenza cases will never result in serious bacterial infections (particularly in nonhospitalized patients), and thus a lot of antibiotic use is unnecessary. As mentioned earlier, unnecessary antibiotic use poses a nonnegligible risk to patients, but it also contributes significantly to rising rates of antibiotic resistance, a major public health issue.

The results from this study highlight that the majority of patients hospitalized with influenza are unlikely to be coinfected with a bacterial pathogen. Thus, it is important for clinicians to appropriately treat patients with antiviral drugs, and ensure that bacterial testing is done when presumptively starting patients on antibiotics. Based on the microbiology results, antibiotics can be stopped if no pathogen is identified or altered to be more appropriate depending on the pathogen found.

Although the findings of this study suggest we need a more thorough analysis of the issue, the results should still aid clinicians by improving their understanding of the likelihood of bacterial coinfection in hospitalized patients with influenza, and thus help them balance the need to minimize patient risks as well as the individual and societal risks of nonessential antibiotic use.

Eili Klein, PhD, is assistant professor in the department of emergency medicine at Johns Hopkins Medicine, Baltimore.

Treatment of patients admitted to the hospital with an upper respiratory infection is often complicated by the lack of diagnostics. Even in cases where a patient has a confirmed case of influenza, there is still the possibility that they may have, or become infected by, a secondary bacterial infection. This leads clinicians to treat patients empirically with antibiotics, which can result in unnecessary antibiotic use among patients without a bacterial infection.

Though antibiotics can be a lifesaving drug, their use is not without risks. Estimates suggest that 20% of patients taking common antibiotics experience some side effect. While most side effects are not life-threatening gastrointestinal effects, other nonnegligible side effects include anaphylactic shock, drug‐induced liver injury, increases in the risk of retinal detachment, serious arrhythmias, and superinfection with resistant bacteria. Antibiotics can also lead to secondary infections, such as Clostridium difficile.

Yet, despite these risks, there has been limited research on the percentage of patients with influenza who actually have a bacterial coinfection. A recent systematic review and meta-analysis conducted by my colleagues at Johns Hopkins University and the Center for Disease Dynamics, Economics & Policy examined the frequency of bacterial coinfection among hospitalized patients with influenza and identified the most common infecting bacterial species.

The findings, published in the journal Influenza and Other Respiratory Viruses, found that in the majority of studies, between 11% and 35% of patients with confirmed influenza had a bacterial coinfection. The most common coinfecting bacteria were found to be Streptococcus pneumoniae and Staphylococcus aureus. Combined, S. pneumoniae and S. aureus accounted for more than 60% of the identified coinfecting bacteria; however, many other bacterial species were found to cause infections as well.

The results suggest that while bacterial infection is common in influenza patients, only about a quarter of patients are likely to be infected. However, the studies were widely heterogeneous, both in patient makeup and results. Analyses of age, setting, enrollment year, study type, study size, and bacterial collection methods did not reveal a source for the heterogeneity in results. Thus, additional factors, such as patient comorbidities or prior antibiotic use, which could not be systematically assessed, may affect the likelihood of coinfection.

Given that the symptoms of influenza and bacterial infection often overlap, correctly diagnosing bacterial coinfection without a laboratory culture can present a challenge. This diagnostic uncertainty leads to significant overuse of antibiotics in patients with influenza alone. Most influenza cases will never result in serious bacterial infections (particularly in nonhospitalized patients), and thus a lot of antibiotic use is unnecessary. As mentioned earlier, unnecessary antibiotic use poses a nonnegligible risk to patients, but it also contributes significantly to rising rates of antibiotic resistance, a major public health issue.

The results from this study highlight that the majority of patients hospitalized with influenza are unlikely to be coinfected with a bacterial pathogen. Thus, it is important for clinicians to appropriately treat patients with antiviral drugs, and ensure that bacterial testing is done when presumptively starting patients on antibiotics. Based on the microbiology results, antibiotics can be stopped if no pathogen is identified or altered to be more appropriate depending on the pathogen found.

Although the findings of this study suggest we need a more thorough analysis of the issue, the results should still aid clinicians by improving their understanding of the likelihood of bacterial coinfection in hospitalized patients with influenza, and thus help them balance the need to minimize patient risks as well as the individual and societal risks of nonessential antibiotic use.

Eili Klein, PhD, is assistant professor in the department of emergency medicine at Johns Hopkins Medicine, Baltimore.

The seasonal influenza vaccination reduced flu-related hospitalizations by 56.8% among people aged 50 and older during a recent flu season, according to a report published in Clinical Infectious Diseases.

Even in the oldest age group – the population with the highest risk of developing flu complications and perhaps the weakest immune response – influenza vaccination prevented serious complications, said Fiona P. Havers, MD, of the influenza division, Centers for Disease Control and Prevention, Atlanta, and her associates.

Data on vaccine efficacy in older adults are sparse, and randomized, placebo-controlled trials to gather evidence would be unethical. Dr. Havers and her colleagues studied the issue using a case-control design, focusing on community-dwelling adults aged 50 years and older during the 2010-2011 flu season. They identified 368 patients across 10 states who were hospitalized for polymerase chain reaction–confirmed influenza and matched them for age and county of residence with 773 control subjects.

Hospitalized case-patients were less likely to have been vaccinated (55%) than were control subjects (63%). Thus, the flu vaccine reduced the risk of hospitalization for influenza by 56.8% overall.

©Wavebreakmedia/Thinkstock

Vaccination reduced hospitalization for influenza by 63.9% in the youngest age group (50-64 years), by 61.0% in the intermediate age group (65-74 years), and by 57.3% in the oldest age group (75 years and older).

These results are similar to those reported in other studies assessing the same time period, including one that evaluated vaccine efficacy in ambulatory adults in the United States and Europe. They also are consistent with the results of observational studies performed during different flu seasons, the investigators said (Clin Infect Dis. 2016 Aug 2. doi: 10.1093/cid/ciw512).

Compared with control subjects, case-patients were more likely to be of nonwhite race, to be of Hispanic ethnicity, to have a lower income, to have had fewer years of education, to have two or more chronic health conditions, to have required recent hospitalization for respiratory problems, to have impaired mobility, and to have lower functional status.

“These findings support current U.S. recommendations for annual influenza vaccination in older adults, especially in adults aged 65 and older who are at higher risk of influenza-associated complications,” Dr. Havers and her associates said.

The Centers for Disease Control and Prevention supported the study. Dr. Havers reported having no relevant financial disclosures; one of her associates reported ties to Genentech, Merck, Novavax, and Pfizer.

The seasonal influenza vaccination reduced flu-related hospitalizations by 56.8% among people aged 50 and older during a recent flu season, according to a report published in Clinical Infectious Diseases.

Even in the oldest age group – the population with the highest risk of developing flu complications and perhaps the weakest immune response – influenza vaccination prevented serious complications, said Fiona P. Havers, MD, of the influenza division, Centers for Disease Control and Prevention, Atlanta, and her associates.

Data on vaccine efficacy in older adults are sparse, and randomized, placebo-controlled trials to gather evidence would be unethical. Dr. Havers and her colleagues studied the issue using a case-control design, focusing on community-dwelling adults aged 50 years and older during the 2010-2011 flu season. They identified 368 patients across 10 states who were hospitalized for polymerase chain reaction–confirmed influenza and matched them for age and county of residence with 773 control subjects.

Hospitalized case-patients were less likely to have been vaccinated (55%) than were control subjects (63%). Thus, the flu vaccine reduced the risk of hospitalization for influenza by 56.8% overall.

©Wavebreakmedia/Thinkstock

Vaccination reduced hospitalization for influenza by 63.9% in the youngest age group (50-64 years), by 61.0% in the intermediate age group (65-74 years), and by 57.3% in the oldest age group (75 years and older).

These results are similar to those reported in other studies assessing the same time period, including one that evaluated vaccine efficacy in ambulatory adults in the United States and Europe. They also are consistent with the results of observational studies performed during different flu seasons, the investigators said (Clin Infect Dis. 2016 Aug 2. doi: 10.1093/cid/ciw512).

Compared with control subjects, case-patients were more likely to be of nonwhite race, to be of Hispanic ethnicity, to have a lower income, to have had fewer years of education, to have two or more chronic health conditions, to have required recent hospitalization for respiratory problems, to have impaired mobility, and to have lower functional status.

“These findings support current U.S. recommendations for annual influenza vaccination in older adults, especially in adults aged 65 and older who are at higher risk of influenza-associated complications,” Dr. Havers and her associates said.

The Centers for Disease Control and Prevention supported the study. Dr. Havers reported having no relevant financial disclosures; one of her associates reported ties to Genentech, Merck, Novavax, and Pfizer.

The seasonal influenza vaccination reduced flu-related hospitalizations by 56.8% among people aged 50 and older during a recent flu season, according to a report published in Clinical Infectious Diseases.

Even in the oldest age group – the population with the highest risk of developing flu complications and perhaps the weakest immune response – influenza vaccination prevented serious complications, said Fiona P. Havers, MD, of the influenza division, Centers for Disease Control and Prevention, Atlanta, and her associates.

Data on vaccine efficacy in older adults are sparse, and randomized, placebo-controlled trials to gather evidence would be unethical. Dr. Havers and her colleagues studied the issue using a case-control design, focusing on community-dwelling adults aged 50 years and older during the 2010-2011 flu season. They identified 368 patients across 10 states who were hospitalized for polymerase chain reaction–confirmed influenza and matched them for age and county of residence with 773 control subjects.

Hospitalized case-patients were less likely to have been vaccinated (55%) than were control subjects (63%). Thus, the flu vaccine reduced the risk of hospitalization for influenza by 56.8% overall.

©Wavebreakmedia/Thinkstock

Vaccination reduced hospitalization for influenza by 63.9% in the youngest age group (50-64 years), by 61.0% in the intermediate age group (65-74 years), and by 57.3% in the oldest age group (75 years and older).

These results are similar to those reported in other studies assessing the same time period, including one that evaluated vaccine efficacy in ambulatory adults in the United States and Europe. They also are consistent with the results of observational studies performed during different flu seasons, the investigators said (Clin Infect Dis. 2016 Aug 2. doi: 10.1093/cid/ciw512).

Compared with control subjects, case-patients were more likely to be of nonwhite race, to be of Hispanic ethnicity, to have a lower income, to have had fewer years of education, to have two or more chronic health conditions, to have required recent hospitalization for respiratory problems, to have impaired mobility, and to have lower functional status.

“These findings support current U.S. recommendations for annual influenza vaccination in older adults, especially in adults aged 65 and older who are at higher risk of influenza-associated complications,” Dr. Havers and her associates said.

The Centers for Disease Control and Prevention supported the study. Dr. Havers reported having no relevant financial disclosures; one of her associates reported ties to Genentech, Merck, Novavax, and Pfizer.

Two children presented with influenza, and both recovered without the need for hospitalization. This scenario would fail to pique the interest of any pediatrician in January. But what about when it happens in July?

In early August, public health authorities in Ohio announced that two children had tested positive for the variant swine influenza virus H3N2v. Both children had direct contact with pigs at the Clark County Fair in late July. Along with a handful of cases diagnosed in Michigan, these represent the first H₃N_2v cases in the United States in 2016.

Influenza viruses that normally circulate in swine are designated as “variant” when they infect humans. According to the Centers for Disease Control and Prevention (CDC), human infections with H₁N_1v, H₁N_2v, and H₃N_2v have been identified in the United States. Influenza A H3N2v viruses carrying the matrix gene from the 2009 H₁N₁ pandemic virus were first detected in pigs in 2010, and in people in the summer of 2011. Since that time, 357 human cases have been reported from 14 states, with nearly 75% occurring in Indiana and Ohio. Most infections occurred after prolonged exposure to pigs at agricultural fairs.

Fortunately, most H₃N_2v infections have been mild: Since July 2012, only 21 individuals have required hospitalization and a single case resulted in death. Notably, though, many of the hospitalizations involved children.

On Aug. 15, the Centers for Disease Control and Prevention released Interim Guidance for Clinicians on Human Infections with Variant Influenza Viruses.

Because variant virus infection is indistinguishable from seasonal influenza or any other virus that cause influenzalike illness (think fever, cough, sore throat), physicians and other frontline providers need to maintain an index of suspicion. The key is eliciting a history of swine exposure in the week before illness onset. Practically, this means asking about direct contact with pigs, indirect contact with pigs, or close contact with an ill person who has had contact with pigs. Kudos to the astute clinicians in Ohio who thought to send the appropriate influenza testing in July.

When variant influenza virus is suspected, a nasopharyngeal swab or aspirate should be obtained for testing at a state public health lab or the CDC. Rapid antigen tests for influenza may be falsely negative in the setting of H₃N_2v infection, just as they may be with seasonal influenza infection. Molecular tests such as reverse transcription polymerase chain reaction (RT-PCR) are likely more sensitive, but cannot distinguish variant influenza A viruses from seasonal influenza A viruses.

The Kentucky State Fair opened on Aug. 18, making the CDC guidance especially timely for health care providers in my area. I called a friend who is a pediatric emergency medicine physician to ask if she and her colleagues were routinely screening patients for encounters of the porcine kind.

“For example, are you asking, ‘Have you been showing, raising or feeding swine? Have you been to the pig barn at the fair?’ ”

When my friend quit laughing, I confessed to her that I had not been doing that routinely either. The exposure history is often the most interesting part of the infectious disease evaluation and in the last month, I’ve asked about exposure to sheep (a risk factor for Q fever), exposure to chickens (a risk factor for Salmonella infections), and exposure to beaver dams (a risk factor for blastomycosis). But I’ve not asked about exposure to pigs.

“The emergency medicine approach is to avoid a lot of viral diagnostic testing unless it is going to impact management,” she said. “Tell me how this changes management of my patient.”

From the patient perspective, making a presumptive diagnosis of H₃N_2v infection would open the door to empiric treatment with antivirals, at least for individuals who are hospitalized, have severe or progressive disease, or who at high risk for complications of influenza. Neuraminidase inhibitors, including oral oseltamivir, inhaled zanamivir, and intravenous peramivir, can be used for treatment of H₃N_2v infections.

From a societal perspective, making the diagnosis gives public health experts the opportunity to investigate and potentially prevent further infections by isolating sick pigs. Human to human transmission of H₃N_2v is rare, but has occasionally occurred in households and in one instance, a child care setting. Careful surveillance of each swine flu case in a human is important to exclude the possibility that the virus has developed the ability to spread efficiently from person to person, creating the risk for an epidemic.

Seasonal influenza vaccine does not prevent infection with variant viruses, so avoidance is key. Those at high risk for complications from influenza infection, including children younger than 5 years of age and those with asthma, diabetes, heart disease, immunocompromised conditions, and neurologic or neurodevelopmental disorders, are urged to avoid pigs and swine barns when visiting fairs where the animals are present. Everyone else needs to follow common sense measures to prevent the spread of infection.

• Don’t take food or drink into pig areas; don’t eat, drink or put anything in your mouth in pig areas.

• Don’t take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.

• Wash your hands often with soap and running water before and after exposure to pigs. If soap and water are not available, use an alcohol-based hand rub.

• Avoid close contact with pigs that look or act ill.

• Take protective measures if you must come in contact with pigs that are known or suspected to be sick. This includes wearing personal protective equipment like protective clothing, gloves, and masks that cover your mouth and nose when contact is required.

• To further reduce the risk of infection, minimize contact with pigs in the pig barn and arenas.

It shouldn’t be surprising that flu viruses spread from pigs to people in the same way that regular seasonal influenza spread from person to person. An infected pig coughs or sneezes influenza-containing droplets, and these droplets are inhaled or swallowed by a susceptible human. That makes avoiding contact with pigs that look or act ill especially important. For the record, a pig with flu might have fever, depression, cough, nasal or eye discharge, eye redness, or a poor appetite.

On the bright side, you can’t get H₃N_2v or any other variant virus from eating properly prepared pork meat. Fairgoers can feel free to indulge in a deep-fried pork chop or one of this year’s featured food items: a basket of French fries topped with smoked pork, cheddar cheese sauce, red onions, jalapeño peppers and barbecue sauce.

Or maybe not. The CDC has a web page devoted to food safety at fairs and festivals. It notes that cases of foodborne illness increase during summer months, and usual safety controls “like monitoring of food temperatures, refrigeration, workers trained in food safety and washing facilities, may not be available when cooking and dining at fairs and festivals.”

The public is urged to seek out “healthy options” from fair vendors first. If healthy options aren’t available, we’re advised to consider bringing food from home to save money and calories.

Sigh. I remember when summer used to be more fun.

Dr. Bryant is a pediatrician specializing in infectious diseases at the University of Louisville, Ky. and Kosair Children’s Hospital, also in Louisville.

Two children presented with influenza, and both recovered without the need for hospitalization. This scenario would fail to pique the interest of any pediatrician in January. But what about when it happens in July?

In early August, public health authorities in Ohio announced that two children had tested positive for the variant swine influenza virus H3N2v. Both children had direct contact with pigs at the Clark County Fair in late July. Along with a handful of cases diagnosed in Michigan, these represent the first H₃N_2v cases in the United States in 2016.

Influenza viruses that normally circulate in swine are designated as “variant” when they infect humans. According to the Centers for Disease Control and Prevention (CDC), human infections with H₁N_1v, H₁N_2v, and H₃N_2v have been identified in the United States. Influenza A H3N2v viruses carrying the matrix gene from the 2009 H₁N₁ pandemic virus were first detected in pigs in 2010, and in people in the summer of 2011. Since that time, 357 human cases have been reported from 14 states, with nearly 75% occurring in Indiana and Ohio. Most infections occurred after prolonged exposure to pigs at agricultural fairs.

Fortunately, most H₃N_2v infections have been mild: Since July 2012, only 21 individuals have required hospitalization and a single case resulted in death. Notably, though, many of the hospitalizations involved children.

On Aug. 15, the Centers for Disease Control and Prevention released Interim Guidance for Clinicians on Human Infections with Variant Influenza Viruses.

Because variant virus infection is indistinguishable from seasonal influenza or any other virus that cause influenzalike illness (think fever, cough, sore throat), physicians and other frontline providers need to maintain an index of suspicion. The key is eliciting a history of swine exposure in the week before illness onset. Practically, this means asking about direct contact with pigs, indirect contact with pigs, or close contact with an ill person who has had contact with pigs. Kudos to the astute clinicians in Ohio who thought to send the appropriate influenza testing in July.

When variant influenza virus is suspected, a nasopharyngeal swab or aspirate should be obtained for testing at a state public health lab or the CDC. Rapid antigen tests for influenza may be falsely negative in the setting of H₃N_2v infection, just as they may be with seasonal influenza infection. Molecular tests such as reverse transcription polymerase chain reaction (RT-PCR) are likely more sensitive, but cannot distinguish variant influenza A viruses from seasonal influenza A viruses.

The Kentucky State Fair opened on Aug. 18, making the CDC guidance especially timely for health care providers in my area. I called a friend who is a pediatric emergency medicine physician to ask if she and her colleagues were routinely screening patients for encounters of the porcine kind.

“For example, are you asking, ‘Have you been showing, raising or feeding swine? Have you been to the pig barn at the fair?’ ”

When my friend quit laughing, I confessed to her that I had not been doing that routinely either. The exposure history is often the most interesting part of the infectious disease evaluation and in the last month, I’ve asked about exposure to sheep (a risk factor for Q fever), exposure to chickens (a risk factor for Salmonella infections), and exposure to beaver dams (a risk factor for blastomycosis). But I’ve not asked about exposure to pigs.

“The emergency medicine approach is to avoid a lot of viral diagnostic testing unless it is going to impact management,” she said. “Tell me how this changes management of my patient.”

From the patient perspective, making a presumptive diagnosis of H₃N_2v infection would open the door to empiric treatment with antivirals, at least for individuals who are hospitalized, have severe or progressive disease, or who at high risk for complications of influenza. Neuraminidase inhibitors, including oral oseltamivir, inhaled zanamivir, and intravenous peramivir, can be used for treatment of H₃N_2v infections.

From a societal perspective, making the diagnosis gives public health experts the opportunity to investigate and potentially prevent further infections by isolating sick pigs. Human to human transmission of H₃N_2v is rare, but has occasionally occurred in households and in one instance, a child care setting. Careful surveillance of each swine flu case in a human is important to exclude the possibility that the virus has developed the ability to spread efficiently from person to person, creating the risk for an epidemic.

Seasonal influenza vaccine does not prevent infection with variant viruses, so avoidance is key. Those at high risk for complications from influenza infection, including children younger than 5 years of age and those with asthma, diabetes, heart disease, immunocompromised conditions, and neurologic or neurodevelopmental disorders, are urged to avoid pigs and swine barns when visiting fairs where the animals are present. Everyone else needs to follow common sense measures to prevent the spread of infection.

• Don’t take food or drink into pig areas; don’t eat, drink or put anything in your mouth in pig areas.

• Don’t take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.

• Wash your hands often with soap and running water before and after exposure to pigs. If soap and water are not available, use an alcohol-based hand rub.

• Avoid close contact with pigs that look or act ill.

• Take protective measures if you must come in contact with pigs that are known or suspected to be sick. This includes wearing personal protective equipment like protective clothing, gloves, and masks that cover your mouth and nose when contact is required.

• To further reduce the risk of infection, minimize contact with pigs in the pig barn and arenas.

It shouldn’t be surprising that flu viruses spread from pigs to people in the same way that regular seasonal influenza spread from person to person. An infected pig coughs or sneezes influenza-containing droplets, and these droplets are inhaled or swallowed by a susceptible human. That makes avoiding contact with pigs that look or act ill especially important. For the record, a pig with flu might have fever, depression, cough, nasal or eye discharge, eye redness, or a poor appetite.

On the bright side, you can’t get H₃N_2v or any other variant virus from eating properly prepared pork meat. Fairgoers can feel free to indulge in a deep-fried pork chop or one of this year’s featured food items: a basket of French fries topped with smoked pork, cheddar cheese sauce, red onions, jalapeño peppers and barbecue sauce.

Or maybe not. The CDC has a web page devoted to food safety at fairs and festivals. It notes that cases of foodborne illness increase during summer months, and usual safety controls “like monitoring of food temperatures, refrigeration, workers trained in food safety and washing facilities, may not be available when cooking and dining at fairs and festivals.”

The public is urged to seek out “healthy options” from fair vendors first. If healthy options aren’t available, we’re advised to consider bringing food from home to save money and calories.

Sigh. I remember when summer used to be more fun.

Dr. Bryant is a pediatrician specializing in infectious diseases at the University of Louisville, Ky. and Kosair Children’s Hospital, also in Louisville.

Two children presented with influenza, and both recovered without the need for hospitalization. This scenario would fail to pique the interest of any pediatrician in January. But what about when it happens in July?

In early August, public health authorities in Ohio announced that two children had tested positive for the variant swine influenza virus H3N2v. Both children had direct contact with pigs at the Clark County Fair in late July. Along with a handful of cases diagnosed in Michigan, these represent the first H₃N_2v cases in the United States in 2016.

Influenza viruses that normally circulate in swine are designated as “variant” when they infect humans. According to the Centers for Disease Control and Prevention (CDC), human infections with H₁N_1v, H₁N_2v, and H₃N_2v have been identified in the United States. Influenza A H3N2v viruses carrying the matrix gene from the 2009 H₁N₁ pandemic virus were first detected in pigs in 2010, and in people in the summer of 2011. Since that time, 357 human cases have been reported from 14 states, with nearly 75% occurring in Indiana and Ohio. Most infections occurred after prolonged exposure to pigs at agricultural fairs.

Fortunately, most H₃N_2v infections have been mild: Since July 2012, only 21 individuals have required hospitalization and a single case resulted in death. Notably, though, many of the hospitalizations involved children.

On Aug. 15, the Centers for Disease Control and Prevention released Interim Guidance for Clinicians on Human Infections with Variant Influenza Viruses.

Because variant virus infection is indistinguishable from seasonal influenza or any other virus that cause influenzalike illness (think fever, cough, sore throat), physicians and other frontline providers need to maintain an index of suspicion. The key is eliciting a history of swine exposure in the week before illness onset. Practically, this means asking about direct contact with pigs, indirect contact with pigs, or close contact with an ill person who has had contact with pigs. Kudos to the astute clinicians in Ohio who thought to send the appropriate influenza testing in July.

When variant influenza virus is suspected, a nasopharyngeal swab or aspirate should be obtained for testing at a state public health lab or the CDC. Rapid antigen tests for influenza may be falsely negative in the setting of H₃N_2v infection, just as they may be with seasonal influenza infection. Molecular tests such as reverse transcription polymerase chain reaction (RT-PCR) are likely more sensitive, but cannot distinguish variant influenza A viruses from seasonal influenza A viruses.

The Kentucky State Fair opened on Aug. 18, making the CDC guidance especially timely for health care providers in my area. I called a friend who is a pediatric emergency medicine physician to ask if she and her colleagues were routinely screening patients for encounters of the porcine kind.

“For example, are you asking, ‘Have you been showing, raising or feeding swine? Have you been to the pig barn at the fair?’ ”

When my friend quit laughing, I confessed to her that I had not been doing that routinely either. The exposure history is often the most interesting part of the infectious disease evaluation and in the last month, I’ve asked about exposure to sheep (a risk factor for Q fever), exposure to chickens (a risk factor for Salmonella infections), and exposure to beaver dams (a risk factor for blastomycosis). But I’ve not asked about exposure to pigs.

“The emergency medicine approach is to avoid a lot of viral diagnostic testing unless it is going to impact management,” she said. “Tell me how this changes management of my patient.”

From the patient perspective, making a presumptive diagnosis of H₃N_2v infection would open the door to empiric treatment with antivirals, at least for individuals who are hospitalized, have severe or progressive disease, or who at high risk for complications of influenza. Neuraminidase inhibitors, including oral oseltamivir, inhaled zanamivir, and intravenous peramivir, can be used for treatment of H₃N_2v infections.

From a societal perspective, making the diagnosis gives public health experts the opportunity to investigate and potentially prevent further infections by isolating sick pigs. Human to human transmission of H₃N_2v is rare, but has occasionally occurred in households and in one instance, a child care setting. Careful surveillance of each swine flu case in a human is important to exclude the possibility that the virus has developed the ability to spread efficiently from person to person, creating the risk for an epidemic.

Seasonal influenza vaccine does not prevent infection with variant viruses, so avoidance is key. Those at high risk for complications from influenza infection, including children younger than 5 years of age and those with asthma, diabetes, heart disease, immunocompromised conditions, and neurologic or neurodevelopmental disorders, are urged to avoid pigs and swine barns when visiting fairs where the animals are present. Everyone else needs to follow common sense measures to prevent the spread of infection.

• Don’t take food or drink into pig areas; don’t eat, drink or put anything in your mouth in pig areas.

• Don’t take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.

• Wash your hands often with soap and running water before and after exposure to pigs. If soap and water are not available, use an alcohol-based hand rub.

• Avoid close contact with pigs that look or act ill.

• Take protective measures if you must come in contact with pigs that are known or suspected to be sick. This includes wearing personal protective equipment like protective clothing, gloves, and masks that cover your mouth and nose when contact is required.

• To further reduce the risk of infection, minimize contact with pigs in the pig barn and arenas.

It shouldn’t be surprising that flu viruses spread from pigs to people in the same way that regular seasonal influenza spread from person to person. An infected pig coughs or sneezes influenza-containing droplets, and these droplets are inhaled or swallowed by a susceptible human. That makes avoiding contact with pigs that look or act ill especially important. For the record, a pig with flu might have fever, depression, cough, nasal or eye discharge, eye redness, or a poor appetite.

On the bright side, you can’t get H₃N_2v or any other variant virus from eating properly prepared pork meat. Fairgoers can feel free to indulge in a deep-fried pork chop or one of this year’s featured food items: a basket of French fries topped with smoked pork, cheddar cheese sauce, red onions, jalapeño peppers and barbecue sauce.

Or maybe not. The CDC has a web page devoted to food safety at fairs and festivals. It notes that cases of foodborne illness increase during summer months, and usual safety controls “like monitoring of food temperatures, refrigeration, workers trained in food safety and washing facilities, may not be available when cooking and dining at fairs and festivals.”

The public is urged to seek out “healthy options” from fair vendors first. If healthy options aren’t available, we’re advised to consider bringing food from home to save money and calories.

Sigh. I remember when summer used to be more fun.

Dr. Bryant is a pediatrician specializing in infectious diseases at the University of Louisville, Ky. and Kosair Children’s Hospital, also in Louisville.

A 66-year-old woman presents as a new patient for a clinic visit. She has a history of Guillain-Barré syndrome 10 years ago. The last immunization she received was a tetanus-diphtheria 12 years ago.

What do you recommend for her to receive over the next year?

A. Pneumococcal 13/Pneumococcal 23/Tdap/influenza vaccines.

B. Pneumococcal 13/Pneumococcal 23/Tdap vaccines.

C. Influenza vaccine.

D. No vaccines.

Guillain-Barré syndrome (GBS) is a rare, acute, immune-mediated polyneuropathy that has an incidence of about 2 cases per 100,000 people each year.¹ Most cases of GBS follow an infectious event (usually an upper respiratory infection or gastrointestinal infection). In 1976, administration of the swine flu vaccine was associated with an up to eightfold increased risk of GBS.^2,3 Many patients who have had GBS have been advised not to – or are fearful to – receive influenza vaccine or any vaccine.

Is there good evidence for patients with a history of GBS to avoid influenza vaccines or vaccinations in general?

The initial concern over the increased risk of GBS following the large-scale influenza vaccination in 1976 has not been realized with subsequent influenza vaccines. In a study by Baxter and colleagues, GBS cases from Kaiser Permanente Northern California from 1995 to 2006 were reviewed.⁴ They looked at whether patients had received influenza vaccine in the 6 weeks prior to GBS, compared with vaccination within the prior 9 months.

The odds ratio for influenza vaccination in the 6 weeks prior to GBS was 1.1 (95% confidence interval, 0.4-3.1). The odds ratio for receiving tetanus diphtheria vaccine in the 6 weeks prior to GBS was 1.4 (95% CI, 0.3-4.5); pneumococcal 23 vaccine, 0.7 (95% CI, 0.1-2.9); and all vaccines combined, 1.3 (95% CI, 0.8-2.3).

Shahed Iqbal, MBBS, et al. looked at the relationship between influenza illness, pneumonia, influenza vaccination, and GBS.⁵ They found that although influenza vaccine coverage increased from 20% to 36% over the study period, there was not an increase in GBS hospitalizations over the same period. There was a significant correlation between hospitalizations for pneumonia and influenza and GBS hospitalizations in the same month.

In a simulation study, Steven Hawken, PhD, and his colleagues concluded that under typical conditions (influenza incidence greater than 5% and vaccine effectiveness greater than 60%), influenza vaccination reduced GBS risk.⁶

There are fewer data on vaccination in patients who have previously had GBS, but there is enough evidence to help guide us.

Roger Baxter, MD, and colleagues, using the database in reference 4, looked at outcome of patients with GBS who received vaccinations subsequent to recovery from GBS.⁷ A total of 279 patient with previous GBS received a total of 989 vaccinations, including 405 trivalent influenza vaccinations. None of the patients with GBS who received vaccinations had a recurrence of GBS.

Krista Kuitwaard, MD, et al. reported identical findings in a survey of patients with a history of GBS or chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).⁸ A total of 245 patients with GBS responded to the survey. A total of 106 GBS patients had received influenza vaccine following their GBS diagnosis (a total of 775 vaccinations in those patients). None of the patients with a history of GBS who received influenza vaccination had a recurrence of their GBS.

The current position of the GBS/CIDP Foundation on vaccination for patients with GBS is as follows: The GBS/CIDP Foundation recommends avoiding immunizations that a GBS patient had received within 6 weeks of developing their initial symptoms.⁹

I think the current evidence is enough to guide us in this issue. Vaccinations, including influenza vaccine, are likely safe for patients with a history of GBS. The recommendation of the GBS/CIDP foundation is reasonable – to avoid immunizations that appeared to have potentially triggered the initial GBS (ones that had been received within 6 weeks of onset of symptoms).

In the case presented above, I think that choice A – receiving all the recommended immunizations – would be appropriate.

References

1. Neuroepidemiology 2011; 36(2):123-33.

2. Am J Epidemiol. 1979 Aug;110(2):105-23.

3. Clin Infect Dis. 2014 Apr;58(8):1149-55.

4. Clin Infect Dis. 2013 Jul;57(2):197-204.

5. Vaccine. 2015 Apr 21;33(17):2045-9.

6. Emerg Infect Dis. 2015 Feb;21(2):224-31.

7. Clin Infect Dis. 2012 Mar;54(6):800-4.

8. J Peripher Nerv Syst. 2009 Dec;14(4):310-5.

9. GBS/CIDP Foundation International, Position on Flu Shots and Vaccinations.

Dr. Paauw is professor of medicine in the division of general internal medicine at the University of Washington, Seattle, and he serves as third-year medical student clerkship director at the University of Washington. Contact Dr. Paauw at [email protected].

A 66-year-old woman presents as a new patient for a clinic visit. She has a history of Guillain-Barré syndrome 10 years ago. The last immunization she received was a tetanus-diphtheria 12 years ago.

What do you recommend for her to receive over the next year?

A. Pneumococcal 13/Pneumococcal 23/Tdap/influenza vaccines.

B. Pneumococcal 13/Pneumococcal 23/Tdap vaccines.

C. Influenza vaccine.

D. No vaccines.

Guillain-Barré syndrome (GBS) is a rare, acute, immune-mediated polyneuropathy that has an incidence of about 2 cases per 100,000 people each year.¹ Most cases of GBS follow an infectious event (usually an upper respiratory infection or gastrointestinal infection). In 1976, administration of the swine flu vaccine was associated with an up to eightfold increased risk of GBS.^2,3 Many patients who have had GBS have been advised not to – or are fearful to – receive influenza vaccine or any vaccine.

Is there good evidence for patients with a history of GBS to avoid influenza vaccines or vaccinations in general?

The initial concern over the increased risk of GBS following the large-scale influenza vaccination in 1976 has not been realized with subsequent influenza vaccines. In a study by Baxter and colleagues, GBS cases from Kaiser Permanente Northern California from 1995 to 2006 were reviewed.⁴ They looked at whether patients had received influenza vaccine in the 6 weeks prior to GBS, compared with vaccination within the prior 9 months.

The odds ratio for influenza vaccination in the 6 weeks prior to GBS was 1.1 (95% confidence interval, 0.4-3.1). The odds ratio for receiving tetanus diphtheria vaccine in the 6 weeks prior to GBS was 1.4 (95% CI, 0.3-4.5); pneumococcal 23 vaccine, 0.7 (95% CI, 0.1-2.9); and all vaccines combined, 1.3 (95% CI, 0.8-2.3).

Shahed Iqbal, MBBS, et al. looked at the relationship between influenza illness, pneumonia, influenza vaccination, and GBS.⁵ They found that although influenza vaccine coverage increased from 20% to 36% over the study period, there was not an increase in GBS hospitalizations over the same period. There was a significant correlation between hospitalizations for pneumonia and influenza and GBS hospitalizations in the same month.

In a simulation study, Steven Hawken, PhD, and his colleagues concluded that under typical conditions (influenza incidence greater than 5% and vaccine effectiveness greater than 60%), influenza vaccination reduced GBS risk.⁶

There are fewer data on vaccination in patients who have previously had GBS, but there is enough evidence to help guide us.

Roger Baxter, MD, and colleagues, using the database in reference 4, looked at outcome of patients with GBS who received vaccinations subsequent to recovery from GBS.⁷ A total of 279 patient with previous GBS received a total of 989 vaccinations, including 405 trivalent influenza vaccinations. None of the patients with GBS who received vaccinations had a recurrence of GBS.

Krista Kuitwaard, MD, et al. reported identical findings in a survey of patients with a history of GBS or chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).⁸ A total of 245 patients with GBS responded to the survey. A total of 106 GBS patients had received influenza vaccine following their GBS diagnosis (a total of 775 vaccinations in those patients). None of the patients with a history of GBS who received influenza vaccination had a recurrence of their GBS.

The current position of the GBS/CIDP Foundation on vaccination for patients with GBS is as follows: The GBS/CIDP Foundation recommends avoiding immunizations that a GBS patient had received within 6 weeks of developing their initial symptoms.⁹

I think the current evidence is enough to guide us in this issue. Vaccinations, including influenza vaccine, are likely safe for patients with a history of GBS. The recommendation of the GBS/CIDP foundation is reasonable – to avoid immunizations that appeared to have potentially triggered the initial GBS (ones that had been received within 6 weeks of onset of symptoms).

In the case presented above, I think that choice A – receiving all the recommended immunizations – would be appropriate.

References

1. Neuroepidemiology 2011; 36(2):123-33.

2. Am J Epidemiol. 1979 Aug;110(2):105-23.

3. Clin Infect Dis. 2014 Apr;58(8):1149-55.

4. Clin Infect Dis. 2013 Jul;57(2):197-204.

5. Vaccine. 2015 Apr 21;33(17):2045-9.

6. Emerg Infect Dis. 2015 Feb;21(2):224-31.

7. Clin Infect Dis. 2012 Mar;54(6):800-4.

8. J Peripher Nerv Syst. 2009 Dec;14(4):310-5.

9. GBS/CIDP Foundation International, Position on Flu Shots and Vaccinations.

Dr. Paauw is professor of medicine in the division of general internal medicine at the University of Washington, Seattle, and he serves as third-year medical student clerkship director at the University of Washington. Contact Dr. Paauw at [email protected].

A 66-year-old woman presents as a new patient for a clinic visit. She has a history of Guillain-Barré syndrome 10 years ago. The last immunization she received was a tetanus-diphtheria 12 years ago.

What do you recommend for her to receive over the next year?

A. Pneumococcal 13/Pneumococcal 23/Tdap/influenza vaccines.

B. Pneumococcal 13/Pneumococcal 23/Tdap vaccines.

C. Influenza vaccine.

D. No vaccines.

Guillain-Barré syndrome (GBS) is a rare, acute, immune-mediated polyneuropathy that has an incidence of about 2 cases per 100,000 people each year.¹ Most cases of GBS follow an infectious event (usually an upper respiratory infection or gastrointestinal infection). In 1976, administration of the swine flu vaccine was associated with an up to eightfold increased risk of GBS.^2,3 Many patients who have had GBS have been advised not to – or are fearful to – receive influenza vaccine or any vaccine.

Is there good evidence for patients with a history of GBS to avoid influenza vaccines or vaccinations in general?

The initial concern over the increased risk of GBS following the large-scale influenza vaccination in 1976 has not been realized with subsequent influenza vaccines. In a study by Baxter and colleagues, GBS cases from Kaiser Permanente Northern California from 1995 to 2006 were reviewed.⁴ They looked at whether patients had received influenza vaccine in the 6 weeks prior to GBS, compared with vaccination within the prior 9 months.

The odds ratio for influenza vaccination in the 6 weeks prior to GBS was 1.1 (95% confidence interval, 0.4-3.1). The odds ratio for receiving tetanus diphtheria vaccine in the 6 weeks prior to GBS was 1.4 (95% CI, 0.3-4.5); pneumococcal 23 vaccine, 0.7 (95% CI, 0.1-2.9); and all vaccines combined, 1.3 (95% CI, 0.8-2.3).

Shahed Iqbal, MBBS, et al. looked at the relationship between influenza illness, pneumonia, influenza vaccination, and GBS.⁵ They found that although influenza vaccine coverage increased from 20% to 36% over the study period, there was not an increase in GBS hospitalizations over the same period. There was a significant correlation between hospitalizations for pneumonia and influenza and GBS hospitalizations in the same month.

In a simulation study, Steven Hawken, PhD, and his colleagues concluded that under typical conditions (influenza incidence greater than 5% and vaccine effectiveness greater than 60%), influenza vaccination reduced GBS risk.⁶

There are fewer data on vaccination in patients who have previously had GBS, but there is enough evidence to help guide us.

Roger Baxter, MD, and colleagues, using the database in reference 4, looked at outcome of patients with GBS who received vaccinations subsequent to recovery from GBS.⁷ A total of 279 patient with previous GBS received a total of 989 vaccinations, including 405 trivalent influenza vaccinations. None of the patients with GBS who received vaccinations had a recurrence of GBS.

Krista Kuitwaard, MD, et al. reported identical findings in a survey of patients with a history of GBS or chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).⁸ A total of 245 patients with GBS responded to the survey. A total of 106 GBS patients had received influenza vaccine following their GBS diagnosis (a total of 775 vaccinations in those patients). None of the patients with a history of GBS who received influenza vaccination had a recurrence of their GBS.

The current position of the GBS/CIDP Foundation on vaccination for patients with GBS is as follows: The GBS/CIDP Foundation recommends avoiding immunizations that a GBS patient had received within 6 weeks of developing their initial symptoms.⁹

I think the current evidence is enough to guide us in this issue. Vaccinations, including influenza vaccine, are likely safe for patients with a history of GBS. The recommendation of the GBS/CIDP foundation is reasonable – to avoid immunizations that appeared to have potentially triggered the initial GBS (ones that had been received within 6 weeks of onset of symptoms).

In the case presented above, I think that choice A – receiving all the recommended immunizations – would be appropriate.

References

1. Neuroepidemiology 2011; 36(2):123-33.

2. Am J Epidemiol. 1979 Aug;110(2):105-23.

3. Clin Infect Dis. 2014 Apr;58(8):1149-55.

4. Clin Infect Dis. 2013 Jul;57(2):197-204.

5. Vaccine. 2015 Apr 21;33(17):2045-9.

6. Emerg Infect Dis. 2015 Feb;21(2):224-31.

7. Clin Infect Dis. 2012 Mar;54(6):800-4.

8. J Peripher Nerv Syst. 2009 Dec;14(4):310-5.

9. GBS/CIDP Foundation International, Position on Flu Shots and Vaccinations.

Dr. Paauw is professor of medicine in the division of general internal medicine at the University of Washington, Seattle, and he serves as third-year medical student clerkship director at the University of Washington. Contact Dr. Paauw at [email protected].

Influenza-attributable mortality was significantly greater in children with influenza B, compared with influenza A, investigators found.

Among those with influenza B, patients aged 10-16 years were most likely to require ICU admission, suggesting this subpopulation may be a target for immunization programs.

©PhotoEuphoria/Thinkstock

The percentage of clinical cases attributed to influenza B range from less than 1% to 44%, according to data published by the Centers for Disease Control and Prevention. However, influenza B is considered less virulent and less capable of causing pandemics and has therefore been less studied and outcomes of its disease less characterized, Dat Tran, MD, MSc, of the Hospital for Sick Children in Canada and his associates reported (Pediatrics. 2016 August. doi: 10.1542/peds.2015-4643).

The purpose of this study was to further understand the prevalence and severity of influenza B cases in comparison with influenza A and to identify pediatric subpopulations most at risk for contracting influenza B.

Children aged 16 years or younger hospitalized from laboratory-confirmed influenza A or B from September 2004 to June 2013 (excluding the pandemic year 2009-2010) were identified through active surveillance of admissions at the 12 pediatric referral centers of the Canadian Immunization Monitoring Program Active (IMPACT), a national surveillance initiative. Information regarding demographics, health status, vaccination status, presenting signs and symptoms, illness severity and mortality, treatment regimens, and ICU admission were collected and analyzed.

Of 4,155 influenza-related admissions during this time period, influenza B accounted for 1,510 (36.3%) cases and influenza A accounted for 2,645 (63.7%) cases.

Children admitted with influenza B tended to be older with a median age 3.9 years (interquartile range, 1.4-7.2), compared with a median of 2 years (IQR, 0.6-4.8 years) for children admitted with influenza A.

Children admitted with influenza B, compared with influenza A, had higher odds of having a vaccine-indicated condition (odds ratio, 1.30; 95% confidence interval, 1.14-1.47) and lower odds of having no underlying medical condition (OR, 0.80; 95% CI, 0.71-0.91), Dr. Tran and his associates reported.

“Compared with influenza A cases, children admitted with influenza B had greater adjusted odds of presenting with headache, abdominal pain, and myalgia, ranging from 1.38 for abdominal pain to 3.19 for myalgia,” they added. “There were no significant differences in antiviral or antibiotic prescription or use between influenza A and B cases.”

There was no significant difference in the proportion of influenza A or B patients admitted to the ICU (12.7% vs. 12.6%). Rather, multivariate modeling identified age and presence of an underlying condition as independent predictors of ICU admission.

Finally, influenza-attributable mortality was significantly greater in children with influenza B (adjusted OR, 2.65; 95% CI, 1.18-5.94). Influenza-attributable mortality occurred in 16 (1.1%) children with influenza B and only 10 (0.4%) children with influenza A. All-cause mortality followed a similar trend.

“Among hospitalized children, influenza A and B infections resulted in similar morbidity while mortality was greater for influenza B disease. Among healthy children hospitalized with influenza B, those aged 10-16 years were most likely to require ICU admission,” the investigators summarized.

“These children should be considered at high risk for complicated influenza B infection and be specifically targeted by immunization programs to receive influenza vaccination, and in particular, a [quadrivalent influenza vaccine],” they recommended.

This study was funded by GlaxoSmithKline Biologicals SA. The Canadian Immunization Monitoring Program Active is funded by the Public Health Agency of Canada. The investigators reported having no relevant disclosures.

Influenza-attributable mortality was significantly greater in children with influenza B, compared with influenza A, investigators found.

Among those with influenza B, patients aged 10-16 years were most likely to require ICU admission, suggesting this subpopulation may be a target for immunization programs.

©PhotoEuphoria/Thinkstock

The percentage of clinical cases attributed to influenza B range from less than 1% to 44%, according to data published by the Centers for Disease Control and Prevention. However, influenza B is considered less virulent and less capable of causing pandemics and has therefore been less studied and outcomes of its disease less characterized, Dat Tran, MD, MSc, of the Hospital for Sick Children in Canada and his associates reported (Pediatrics. 2016 August. doi: 10.1542/peds.2015-4643).

The purpose of this study was to further understand the prevalence and severity of influenza B cases in comparison with influenza A and to identify pediatric subpopulations most at risk for contracting influenza B.

Children aged 16 years or younger hospitalized from laboratory-confirmed influenza A or B from September 2004 to June 2013 (excluding the pandemic year 2009-2010) were identified through active surveillance of admissions at the 12 pediatric referral centers of the Canadian Immunization Monitoring Program Active (IMPACT), a national surveillance initiative. Information regarding demographics, health status, vaccination status, presenting signs and symptoms, illness severity and mortality, treatment regimens, and ICU admission were collected and analyzed.

Of 4,155 influenza-related admissions during this time period, influenza B accounted for 1,510 (36.3%) cases and influenza A accounted for 2,645 (63.7%) cases.

Children admitted with influenza B tended to be older with a median age 3.9 years (interquartile range, 1.4-7.2), compared with a median of 2 years (IQR, 0.6-4.8 years) for children admitted with influenza A.

Children admitted with influenza B, compared with influenza A, had higher odds of having a vaccine-indicated condition (odds ratio, 1.30; 95% confidence interval, 1.14-1.47) and lower odds of having no underlying medical condition (OR, 0.80; 95% CI, 0.71-0.91), Dr. Tran and his associates reported.

“Compared with influenza A cases, children admitted with influenza B had greater adjusted odds of presenting with headache, abdominal pain, and myalgia, ranging from 1.38 for abdominal pain to 3.19 for myalgia,” they added. “There were no significant differences in antiviral or antibiotic prescription or use between influenza A and B cases.”

There was no significant difference in the proportion of influenza A or B patients admitted to the ICU (12.7% vs. 12.6%). Rather, multivariate modeling identified age and presence of an underlying condition as independent predictors of ICU admission.

Finally, influenza-attributable mortality was significantly greater in children with influenza B (adjusted OR, 2.65; 95% CI, 1.18-5.94). Influenza-attributable mortality occurred in 16 (1.1%) children with influenza B and only 10 (0.4%) children with influenza A. All-cause mortality followed a similar trend.

“Among hospitalized children, influenza A and B infections resulted in similar morbidity while mortality was greater for influenza B disease. Among healthy children hospitalized with influenza B, those aged 10-16 years were most likely to require ICU admission,” the investigators summarized.

“These children should be considered at high risk for complicated influenza B infection and be specifically targeted by immunization programs to receive influenza vaccination, and in particular, a [quadrivalent influenza vaccine],” they recommended.

This study was funded by GlaxoSmithKline Biologicals SA. The Canadian Immunization Monitoring Program Active is funded by the Public Health Agency of Canada. The investigators reported having no relevant disclosures.

Influenza-attributable mortality was significantly greater in children with influenza B, compared with influenza A, investigators found.

Among those with influenza B, patients aged 10-16 years were most likely to require ICU admission, suggesting this subpopulation may be a target for immunization programs.

©PhotoEuphoria/Thinkstock

The percentage of clinical cases attributed to influenza B range from less than 1% to 44%, according to data published by the Centers for Disease Control and Prevention. However, influenza B is considered less virulent and less capable of causing pandemics and has therefore been less studied and outcomes of its disease less characterized, Dat Tran, MD, MSc, of the Hospital for Sick Children in Canada and his associates reported (Pediatrics. 2016 August. doi: 10.1542/peds.2015-4643).

The purpose of this study was to further understand the prevalence and severity of influenza B cases in comparison with influenza A and to identify pediatric subpopulations most at risk for contracting influenza B.

Children aged 16 years or younger hospitalized from laboratory-confirmed influenza A or B from September 2004 to June 2013 (excluding the pandemic year 2009-2010) were identified through active surveillance of admissions at the 12 pediatric referral centers of the Canadian Immunization Monitoring Program Active (IMPACT), a national surveillance initiative. Information regarding demographics, health status, vaccination status, presenting signs and symptoms, illness severity and mortality, treatment regimens, and ICU admission were collected and analyzed.

Of 4,155 influenza-related admissions during this time period, influenza B accounted for 1,510 (36.3%) cases and influenza A accounted for 2,645 (63.7%) cases.

Children admitted with influenza B tended to be older with a median age 3.9 years (interquartile range, 1.4-7.2), compared with a median of 2 years (IQR, 0.6-4.8 years) for children admitted with influenza A.

Children admitted with influenza B, compared with influenza A, had higher odds of having a vaccine-indicated condition (odds ratio, 1.30; 95% confidence interval, 1.14-1.47) and lower odds of having no underlying medical condition (OR, 0.80; 95% CI, 0.71-0.91), Dr. Tran and his associates reported.

“Compared with influenza A cases, children admitted with influenza B had greater adjusted odds of presenting with headache, abdominal pain, and myalgia, ranging from 1.38 for abdominal pain to 3.19 for myalgia,” they added. “There were no significant differences in antiviral or antibiotic prescription or use between influenza A and B cases.”

There was no significant difference in the proportion of influenza A or B patients admitted to the ICU (12.7% vs. 12.6%). Rather, multivariate modeling identified age and presence of an underlying condition as independent predictors of ICU admission.

Finally, influenza-attributable mortality was significantly greater in children with influenza B (adjusted OR, 2.65; 95% CI, 1.18-5.94). Influenza-attributable mortality occurred in 16 (1.1%) children with influenza B and only 10 (0.4%) children with influenza A. All-cause mortality followed a similar trend.

“Among hospitalized children, influenza A and B infections resulted in similar morbidity while mortality was greater for influenza B disease. Among healthy children hospitalized with influenza B, those aged 10-16 years were most likely to require ICU admission,” the investigators summarized.

“These children should be considered at high risk for complicated influenza B infection and be specifically targeted by immunization programs to receive influenza vaccination, and in particular, a [quadrivalent influenza vaccine],” they recommended.

This study was funded by GlaxoSmithKline Biologicals SA. The Canadian Immunization Monitoring Program Active is funded by the Public Health Agency of Canada. The investigators reported having no relevant disclosures.