As of the end of last week 159 people in nine states had been identified with H3N2 influenza virus infections this year. Most of the recent cases have occurred after contact with pigs at county or state fairs.

The Pennsylvania Department of Health (PDH) reports four confirmed and six probable human cases of influenza due to the H3N2v strain. The Pennsylvania cases occurred among youth participants in the Huntingdon County Fair, Aug. 5-11. PDH reports no hospitalizations, and although the investigation is ongoing, there is no evidence of the strain spreading from person-to-person.

This is the same virus that recently caused illness in several other states, particularly in Indiana (138 cases) and Ohio (72 cases), mostly among children who were exhibitors at or attended agricultural fairs.

Also last week, the Wisconsin State Laboratory of Hygiene confirmed the first two cases of H3N2v influenza virus infection in that state. One case involved a teenager exhibiting pigs at the Wisconsin State Fair; the other involved a state fair worker.

H3N2 influenza viruses occur in pigs but usually do not infect humans, according to the U.S. Centers for Disease Control and Prevention (CDC).

Health experts believe flu viruses spread from infected pigs to humans in the same way seasonal influenza viruses spread between people: mainly through infected droplets created when an infected pig coughs or sneezes.

According to CDC, some evidence indicates people also might become infected by touching something that has virus on it and then touching their mouth or nose. A third way people may get infected is to inhale dust containing the flu virus.

Health officials point out there is no risk of exposure to influenza from handling or eating pork products.

Several state fairs, including Minnesota, Kansas and Texas, have yet to get underway and health officials in those states and others are increasing messaging to the public.

National Pork Board (NPB) has a fact sheet called “INFLUENZA: Pigs, People and Public Health.”

To help clarify the too frequent mis-labeling of influenza exposures as “swine flu” NPB has another fact sheet entitled “Understanding influenza virus naming.”

 Additional information on the H3N2 virus and preventative steps can be found on the CDC website.

Also last week, University of Florida infectious disease experts released a study that found that several pigs exhibited at U.S. state fair competitions in 2009 were infected with influenza virus, despite their healthy appearance. You can find more on that study here.