Information on Swine/Variant Influenza
Swine influenza is a respiratory disease of pigs caused by type A influenza viruses that regularly cause outbreaks of influenza in pigs. Influenza viruses that commonly circulate in swine are called “swine influenza viruses” or “swine flu viruses.” Like human influenza viruses, there are different subtypes and strains of swine influenza viruses. The main swine influenza viruses circulating in U.S. pigs in recent years have been, swine triple reassortant (tr) H1N1 influenza virus, trH3N2 virus, and trH1N2 virus.
- CDC Reports Two Human Infections with Flu Viruses From Pigs Friday, August 4, 2023
- Influenza Risk Assessment Tool (IRAT) Thursday, July 6, 2023
- CDC Awaits Clinical Specimen from Fatal Variant Flu Case in Brazil Friday, June 23, 2023

CDC data on the most current case counts for variant flu virus infections in humans reported in the United States.
MoreThe Junior Disease Detectives: Operation Outbreak Graphic Novel
CDC has partnered with the U.S. Department of Agriculture (USDA) and 4-H to develop “The Junior Disease Detectives: Operation Outbreak,” a graphic novel intended to educate youth audiences about variant flu and the real disease detective work conducted by public and animal health experts when outbreaks of infectious diseases occur.