New research from MIT suggests that influenza viruses spread by waterfowl may be reaching the US mainland through Alaska. 

In 2014 and 2015, an outbreak of H5N8, H5N1, and H5N2 influenza affected poultry farms in North America, resulting in the culling of nearly 50 million chickens and turkeys. The new study finds that an epidemic flu strain, which originated in Southeast Asia, was most likely carried into Alaska by wild migratory birds. In Alaska, the viruses mingled with local  and eventually evolved into the deadly strains that spread south to poultry farms in Washington, Oregon, and California.

“We think there’s strong evidence that those viruses moved through the Bering strait through wild bird populations and began a process of evolution that ended up with them infecting poultry populations and becoming a big agricultural issue,” says Jonathan Runstadler, an assistant professor of biological engineering and comparative medicine at MIT and the senior author of the study.