#16,492
As the two maps above illustrate, the incidence of influenza has increased markedly across the nation over the last reporting week, with the number of states reporting high or very high levels of flu jump from 20 in week 51 to 31 in week 52.
ILI rates remain above the National baseline (see chart above) for the 4th week in a row, and continue to rise sharply.
In Week 53 influenza A makes up more than 99% of the flu cases detected, and H3N2 makes up > 99% of the influenza A viruses identified.
While early concerns have been raised over this year's vaccine match to the H3N2 virus in circulation (see Preprint: Antigenic & Virological properties of an H3N2 Variant That Will Likely Dominate the 2021-2022 Influenza season) - it is still expected to lower the risks of severe illness - and is very much worth getting.
- Influenza activity is increasing, with the eastern and central parts of the country seeing the majority of viruses reported and the western part of the country reporting lower levels of influenza virus circulation.
- The majority of influenza viruses detected are A(H3N2). Earlier in the season, most influenza A(H3N2) infections occurred among children and young adults ages 5-24 years; however, in recent weeks, the proportion of infections occurring among other age groups, especially adults age 25 years and older, has been increasing.
- Most of the H3N2 viruses so far are genetically closely related to the vaccine virus, but there are some antigenic differences that have developed as H3N2 viruses have continued to evolve.
- The percentage of outpatient visits due to respiratory illness continues to increase and is above the national baseline. Influenza is contributing to levels of respiratory illness, but other respiratory viruses are also circulating. The relative contribution of influenza varies by location.
- Hospitalizations for influenza continue to increase. The cumulative hospitalization rate in the FluSurv-NET system is higher than the rate for the entire 2020-2021 season, but lower than the rate seen at this time during the four seasons preceding the COVID-19 pandemic.
- The flu season is just getting started. There’s still time to get vaccinated. An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
- There are early signs that flu vaccination uptake is down this season compared to last.
- Flu vaccines are available at many different locations, including pharmacies and health departments. With flu activity just getting started, there is still time to benefit from flu vaccination this season. Visit www.vaccines.gov to find a flu vaccine near you.
- There are also flu antiviral drugs that can be used to treat flu illness.
Given that hospitals and emergency services are likely to overwhelmed in the months ahead due to the dual circulation of influenza and COVID (see More U.S. Hospitals Inch Towards Invoking Crisis Standards of Care), getting the COVID vaccine (and booster), the flu vaccine, the wearing of face masks,and social distancing can all help reduce your risk of needing medical services in the weeks and months ahead.
