US Influenza Activity Has Increased in February

Influenza activity in the United States has hit a new high for the season, although a new weekly flu report from the US Centers for Disease Control and Prevention (CDC) says the country continues to have a low-severity flu season. The FluView report for week 7—which ended on February 16, 2019—notes that the percentage of outpatient visits for influenza-like illness (ILI) rose to 5.1%, up from 4.8% the previous week. Although this is a new high for the 2018-2019 flu season, rates for ILI, flu hospitalizations, and deaths attributed to pneumonia and influenza continue to remain low when compared with recent seasons. “Whereas influenza A(H1N1)pdm09 viruses predominated in most areas of the country, influenza A(H3N2) viruses have predominated in the southeastern United States, and in recent weeks accounted for a growing proportion of influenza viruses detected in several other regions,” the authors of a recent update published on February 15 in the CDC’s Morbidity and Mortality Weekly Report. In the report the CDC estimates that from October 1, 2018, to February 2, 2019, influenza virus infection has caused 13.2 million to 15.2 million symptomatic illnesses, 6.17 million to 7.22 million medical visits, 155,000 to 186,000 hospitalizations, and 9600 to 15,900 deaths. The CDC has also released its interim estimates for the seasonal influenza vaccine effectiveness so far this season, reporting that the flu shot has been about 47% effective overall at preventing flu illness and 46% effective against the dominant influenza A(H1N1)pdm09 strain. The findings are based on data from the US Influenza Vaccine Effectiveness Network, which includes information collected from 3254 children and adults with acute respiratory illness from November 23, 2018, to February 2, 2019. The flu vaccine was 38% effective overall during the 2017-2018 flu season, and prevented an estimated 7.1 million flu illnesses and 8000 deaths according to a recent study. **Source:** https://www.cdc.gov/flu/weekly/index.htm