Outbreaks of avian influenza in the United States should drop off dramatically with the emergence of summer weather, but the poultry industry should still be cautious as the virus will have a good likelihood of returning in the fall, USDA officials said.

Speaking during a USDA-hosted media call on April 22, USDA Chief Veterinary Officer John Clifford and USDA Southeast Poultry Research Director David Swayne spoke of the virus that has caused the deaths of millions of birds – including commercial turkeys and layer hens – in the United States in 2015.

“We know this virus doesn’t like the heat. When it gets up to a certain level of temperature, this virus doesn’t survive usually. It does like the cooler temperatures,” said Clifford.

Swayne added that it is not just the heat that can kill avian influenza virus. While the temperatures tend to rise during the spring and summer, the amount of sunlight also increases. And the ultraviolet light in sunshine will kill influenza viruses, whether it is on dust, in the air or on individual surfaces.

The amount of humidity also plays a factor, according to Swayne, because dryness helps reduce the life of avian influenza virus.

Avian influenza likely to return in fall

While more southern states like Missouri, Kansas and Arkansas have seen cases of avian influenza, the most recent cases have been further north, in states including Minnesota, Wisconsin, Iowa, North Dakota and South Dakota. Two recent cases have also appeared in Ontario.


Wild birds, who are believed to have been spreading the virus, are returning to the north.

Swayne said he was not sure whether the birds would bring the virus back during their next migration to the South. However, he indicated it is likely, and that the poultry industry needs to be prepared.

Potential for avian influenza in the Eastern US

To date, avian influenza cases have only been detected within the Pacific, Central and Mississippi flyways, but people should not rule out the possibility of the virus spreading to the Atlantic flyway. The furthest east the virus has been confirmed in North America in 2015 has been near Woodstock, Ontario, north of Lake Erie.

“Thse birds don’t just stay in one flyway. There is some crossover. We would anticipate if we see the virus again in the fall, we are likely to see it in all four flyways,” said Clifford.

See a related story about how Swayne and Clifford discussed the USDA’s efforts to develop a vaccine for avian influenza.