News from the FDA/CDC

Flu activity increases for third straight week


For the second time during the 2019-2020 flu season, activity measures have climbed into noteworthy territory.

Influenza-like illness activity level, week ending Feb. 1, 2020

The proportion of outpatient visits for influenza-like illness (ILI) reached its highest December level, 7.1%, since 2003 and then dropped for 2 weeks. Three weeks of increases since then, however, have the outpatient-visit rate at 6.7% for the week ending Feb. 1, 2020, the Centers for Disease Control and Prevention reported. The baseline rate for the United States is 2.4%.

That rate of 6.7% is already above the highest rates recorded in eight of the last nine flu seasons, and another increase could mean a second, separate trip above 7.0% in the 2019-2020 season – something that has not occurred since national tracking began in 1997, CDC data show.

Those same data also show that, from 1997-1998 to 2018-2019, the United States has spent a total of 11 weeks above the 7.0% mark for ILI-related visits.

Another important measure on the rise, the proportion of respiratory specimens testing positive for influenza, reached a new high for the season, 29.8%, during the week of Feb. 1, the CDC’s influenza division said.

Tests at clinical laboratories also show that predominance is continuing to switch from type B (45.6%) to type A (54.4%), the influenza division noted. Overall predominance for the season, however, continues to favor type B, 59.3% to 40.7%.

The percentage of deaths caused by pneumonia and influenza, which passed the threshold for epidemic of 7.2% back in early January, has been trending downward for the last 3 weeks and was 7.1% as of Feb. 1, according to the influenza division.

ILI-related deaths among children continue to remain high, with a total count of 78 for the season after another 10 deaths were reported during the week ending Feb. 1, the CDC reported. Comparable numbers for the last three seasons are 44 (2018-2019), 97 (2017-2018), and 35 (2016-2017).

The CDC estimates put the total number of ILIs at around 22 million for the season so far, leading to 210,000 hospitalizations. The agency said that it expects to release estimates of vaccine effectiveness later this month.

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