Follow along with us this respiratory season for updates every two weeks.

The decrease in influenza virus positivity has been primarily driven by decreases in influenza A virus detection. Of the 7.9% positivity rate for the week ending March 15^th, 2025, influenza B virus made up 2.6% of cases while influenza A virus was responsible for the remainder. At the peak of influenza virus activity, influenza A virus was responsible for 22.0% of cases while influenza B virus was only 1.4%. While influenza virus activity is decreasing nationally, some states are still experiencing high levels of influenza virus activity, including New Hampshire (20.0%), Delaware (24.0%), New Jersey (15.0%) and Washington D.C. (16.1%).

We appear to be entering the spring respiratory virus season, where human metapneumovirus, parainfluenza virus, and rhinovirus/enterovirus become more prevalent. Human metapneumovirus is typically a mild respiratory infection that occurs in children, with re-infection occurring throughout life. This virus typically has peak infectivity in March, and it can cause acute asthma flare-ups both in children and adults¹.

This report reflects observed trends in HealthTrackRx testing positivity data, does not convey medical advice, and is provided for informational purposes only.  Individuals experiencing respiratory symptoms should consult with their healthcare provider.

1. Rudd PA, Thomas BJ, Zaid A, MacDonald M, Kan-O K, Rolph MS, Soorneedi AR, Bardin PG, Mahalingam S. Role of human metapneumovirus and respiratory syncytial virus in asthma exacerbations: where are we now? Clin Sci (Lond). 2017 Jun 30;131(14):1713-1721. doi: 10.1042/CS20160011. PMID: 28667069.