Past Outbreaks

Swine influenza viruses can circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans.

While swine flu viruses do not usually infect humans, rare human infections have occurred. When this happens, these viruses are called “variant viruses.” Most commonly, human infections with variant viruses have occurred in people exposed to infected pigs (e.g., children near pigs at a fair or workers in the swine industry).

• Reported Infections with Variant Influenza Viruses in the United States since 2005
• H3N2v Case Count