Before 2012, outbreaks of so-called “influenza A variant” infections in the U.S. only popped up once in a while in the medical literature. The strain normally infected pigs and was rarely seen in humans. Then, in 2012, healthcare workers across the U.S. reported 309 human cases of influenza A (H3N2) variant, also known as H3N2v. Sixteen people were hospitalized, and one woman in Ohio died. Researchers think there were likely thousands of cases of H3N2v that year that went unreported or unconfirmed.
Epidemiological studies indicated nearly all of the people who became sick with H3N2v in 2012 caught it from prize piggies shown at county fairs. However, this kind of research only draws conclusions based on people’s sickness and their behaviors. Now, a new, in-depth study of the genetics of H3N2v in swine and humans in Ohio shows the epidemiological studies were right.
Samples of flu viruses taken from pigs and from people in Ohio during the 2012 outbreak were genetically close to one another, according to the study, which involved swabbing the insides of 834 pigs’s noses. (We’ve decided pig boogers = poogers.) That means the outbreak really did come straight from infected pigs. In addition, all of the cases recorded across the state were more than 99.5 percent similar to one another genetically, indicating that it was just one flu strain that took residence in humans and swine alike.
Swine are susceptible to avian, human and swine flus, which makes them a great meet-market for flu viruses to exchange genetic material.
It’s a little funny to think of getting a flu from a pig at the county fair. That’s not exactly the kind of scene you imagine for the beginning of a sci-fi movie about the next big pandemic. Yet pigs are a crucial petri dish in which influenza viruses evolve. Swine are susceptible to avian, human and swine flus, and these virus can circulate inside pigs for varying lengths of time with no signs of illness. This makes them great meet-markets for flu viruses to exchange genetic material. The H1N1 flu that reached pandemic proportions in 2009 first spent some time circulating among pigs in Asia, Europe and North America.
Luckily, H3N2v doesn’t readily move between people, which limits its ability to spread. People mostly catch it directly from swine. The U.S. Centers for Disease Control and Prevention recommend that people who are susceptible to complications from the flu — such as young kids, older adults and pregnant women — avoid pig barns at fairs. Keeping away from sick-looking pigs is important, but not adequate. Many of the pigs found to be carrying H3N2v looked healthy. The CDC also has a bunch of recommendations about hand-washing and not eating in pig barns, which doesn’t sound appetizing, anyway, but I can imagine if you just nabbed yourself some funnel cake, you might be tempted. (Don’t do it!) Nobody recommends avoiding agricultural fairs altogether. You can’t get H3N2v from eating pork.
The study did find the virus was pretty widespread. Out of 40 unnamed fairs where researchers swabbed piggy noses, 10 had more than one animal that carried H3N2v. Seven of those 10 fairs were associated with reported human illnesses. And even more scary, six of those seven fairs didn’t have any sick-looking pigs. Public health departments should monitor pigs closely for influenza A viruses, the study authors wrote in their paper, which was published in the September issue of the journal Emerging Infectious Diseases. That probably means more investigators gathering poogers at fairs.
Fortunately, the number of H3N2v infectious seems to have dropped since 2012. In 2013, authorities reported just 19 human cases.
