News from the FDA/CDC

H3N2 putting a damper on flu season’s departure


The decline of influenza activity remains slow, largely “driven by a wave of H3N2 virus activity” in recent weeks, according to the Centers for Disease Control and Prevention.

Influenza-like illness activity level, week ending March 16, 2019

Fewer states reported the highest level of influenza-like illness (ILI) activity on the CDC’s 1-10 scale for the week ending March 16, but the national proportion of outpatient visits for ILI was 4.4% for the second consecutive week, the CDC’s influenza division reported March 22. The outpatient-visit figure for the week ending March 9 was originally reported as 4.5% last week, but it has been revised down to 4.4% this week.

Another measure of activity – the percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories – actually increased slightly during the week ending March 16, the CDC noted.

For the current week, there were 26 states in the high (8-10) range of activity – 20 states were at level 10 and another 6 states were at level 8 – compared with the previous week, when 21 states were at level 10 and 30 states were in the high range, the CDC’s Outpatient ILI Surveillance Network reported.

There were eight ILI-related deaths in children reported during the week ending March 16, seven of which occurred in previous weeks. The total for the 2018-2019 season so far is 76, the CDC said.

New preliminary estimates on influenza’s burden nationally put the total number of deaths at 25,000-41,500 since the beginning of the season on Oct. 1, 2018. There also have been 375,000-454,000 flu-related hospitalizations, 13.2 million to 15.4 million medical visits, and 28.5 to 32.8 million individual illnesses, the CDC said.

Since the CDC “expects flu activity to remain elevated for a number of weeks,” it continues to recommend flu vaccination and the use of influenza antiviral drugs as “an important second line of defense that can be used to treat flu illness. H3N2 viruses are typically associated with more severe illness in older adults, and flu vaccine may protect less well against H3N2 illness in older adults, making prompt treatment with flu antivirals in this age group especially important during the current period of H3N2 predominance.”

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