The U.S. Geological Survey (USGS) has released additional evidence that western Alaska remains a hot spot for avian influenza to enter North America.

The new report announces that while no cases of highly pathogenic avian influenza have been found in Alaska, the state remains an important area to monitor due to migratory bird flyways from North America and Eurasia that overlap the region.

“Our past research in western Alaska has shown that while we have not detected the highly pathogenic avian influenza virus, up to 70 percent of the other avian influenza viruses isolated in this area were found to contain genetic material from Eurasia, providing evidence for high levels of intercontinental viral exchange,” said Andy Ramey, a scientist with the USGS and lead author of the recent report. “This is because Asian and North American migratory flyways overlap in western Alaska.”

Past research by the USGS, found low pathogenic H9N2 viruses in an Emperor Goose and a Northern Pintail. Both viruses were nearly identical genetically to viruses found in wild bird samples from Lake Dongting, China and Cheon-su Bay, South Korea. 

“These H9N2 viruses are low pathogenic and not known to infect humans, but similar viruses have been implicated in disease outbreaks in domestic poultry in Asia,” said Ramey. 

In the new report, the USGS collaborated with the Yukon Kuskokwim Health Corporation in Bethel, Alaska, and the Southeastern Cooperative Wildlife Disease Study in Athens, Georgia to obtain and test bird samples from Alaska Native subsistence hunters during spring of 2015. Hunters provided researchers with over 1,000 swabs from harvested water birds, the primary hosts of avian influenza viruses. 

In 2015, the USGS published an article describing the introduction of highly pathogenic avian influenza into North America at the end of 2014, likely via migratory birds that migrated through Alaska. However, highly pathogenic avian influenza was never documented in Alaska. The highly pathogenic viruses spread throughout parts of the western and Midwestern U.S., impacting more than 48 million birds.

This fall, the USGS will sample wild birds at Izembek National Wildlife Refuge. Most of those samples will come from hunters. 

The new report is entitled, “Surveillance for Eurasian-origin and intercontinental reassortant highly pathogenic influenza A viruses in Alaska, spring and summer 2015” and is published in Virology Journal.