How Do Flu Viruses In Pigs Differ From Flu Viruses In Humans?

June 3, 2009 -- Question:How do flu viruses in pigs differ from flu viruses in humans?

Answer: Pigs, a lot like humans, are a natural host of influenza. And pigs, again, very much like humans -- it's a seasonal disease where it tends to be a little bit more year-round in pigs. If you look at the actual viruses that are present within swine population somewhat surprisingly they're actually very similar to what we see in humans.

In humans, we have two types of influenza A virus. We have H1N1s and H3N2s, and those two types of flu viruses are also in pigs in different parts of the world. What is different about influenza in pigs than in, for instance humans, is that in pigs the viruses actually differ depending on where you are in the world. So the viruses that are circulating in Europe and Asia are actually genetically, biologically different to the ones we see in North America and so on. And that's something we don't see in humans, where typically when a virus comes into the human population it spreads on a global scale. So, influenza in pigs is certainly a lot more geographically defined.