Update : Influenza Activity — United States and Worldwide, May 21–September 23, 2017

Abstract

© 2017, Department of Health and Human Services. All rights reserved. What is already known about this topic?CDC collects, compiles, and analyzes data on influenza activity year-round in the United States. Timing of influenza activity and predominant circulating influenza viruses vary by season. What is added by this report? Worldwide, influenza activity during May 21-September 23, 2017, followed typical seasonality and in the United States overall, low levels of seasonal influenza activity were detected. The majority of influenza viruses genetically and antigenically characterized at CDC were similar to the reference viruses representing the recommended components for the 2017-18 vaccine. A small subset of antigenically distinct influenza B/Victoria viruses was detected. What are the implications for public health practice? In the United States, an annual influenza vaccination is recommended for all persons aged ≥6 months and can reduce the likelihood of becoming ill with influenza and transmitting the virus to others. Annual influenza vaccination offers optimal protection regardless of whether the vaccine composition has changed since the previous season, because immunity wanes over time. Although vaccination is the best method for preventing and reducing the impact of influenza, antiviral medications are an important adjunct. Early treatment with influenza antiviral medications is recommended for patients with confirmed or suspected influenza (either seasonal influenza or novel influenza virus infection) who have severe, complicated, or progressive illness; who require hospitalization; or who are at high risk for influenza-related complications. Testing for seasonal influenza viruses and monitoring for novel influenza A virus infections should continue year-round.