January 17, 2023
This influenza season activity started aggressively in October 2022 with positivity rates passing 5% of tested specimens in October and peaking over 25% in December. Fortunately, the rates are starting to decline rapidly in 2023. Whether the positivity rate continues to decline is questionable given that children are back to school now after the holidays break and social gatherings will increase throughout February due to football and Valentine's day. And a late influenza B wave is still possible.
This influenza season seemed very concerning at the beginning due to much earlier peak of the cumulative rate of hospitalization compared to previous influenza seasons over the last decade. However, given that the rate of positivity is declining rapidly, it is likely that hospitalization rate will plateau and even decline over the next couple of weeks as long as the positivity rate continues to decline.
CDC estimates that, so far this season, there have been at least 24 million illnesses, 260,000 hospitalizations, and 16,000 deaths from influenza. Now, the good news is that the circulating influenza viruses seem to match the current influenza vaccines. Circulating influenza vaccines consisted of 98.6% influenza A and only 1.4% influenza B. Of influenza A viruses detected and subtyped during week 1, 77% were influenza A(H3N2) and 23% were influenza A(H1N1). Subclade 3C.2a1b, subgroup 2a.2 made up 99.9% of H3N2 subtype, and subclade 6B.1A, subgroup 5a.2 made up 98.6% of H1N1 subtype. The majority of influenza viruses tested are in the same genetic subclade as and antigenically similar to the influenza viruses included in this season’s influenza vaccine.
An annual influenza vaccine is the best way to protect against flu. Vaccination helps prevent infection and can also prevent serious outcomes in people who get vaccinated but still get sick with flu. CDC recommends that everyone ages 6 months and older without contraindications get an annual influenza vaccine as long as flu activity continues.
See more details at: https://youtu.be/Q3Gknp4Xpe4
Alireza FakhriRavari, PharmD, BCPS, BCIDP, AAHIVP is an Assistant Professor of Infectious Diseases at Loma Linda University School of Pharmacy.
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