On Aug. 4, 2023, the U.S. Centers for Disease Control and Prevention (CDC) reported the first two U.S. human infections with swine flu viruses in 2023. These human infections were caused by two different types of flu viruses that normally spread among pigs, and they occurred in two people who attended different agricultural fairs in Michigan and had exposure to pigs.

These venues can increase the risk that flu viruses will spread among pigs and between pigs and people.