On Aug. 23, 2024, the U.S. Centers for Disease Control and Prevention (CDC) reported that two human infections with novel influenza A viruses were reported in Ohio and Pennsylvania.

One infection with an influenza A(H1N1) variant (A(H1N1)v) virus was reported by the Ohio Department of Health and the other infection with an influenza A(H1N2)v was reported by the Pennsylvania Department of Health. Both patients were >18 years of age, and were briefly hospitalized due to underlying medical conditions and had recovered.

The CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local public health laboratories according to the Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines. To-date, the CDC had genetically characterized 5,295 influenza viruses collected since October 1, 2023.