DOUGLAS, Ore. — Several cases of a highly pathogenic avian influenza strain have been confirmed in states along the West Coast, causing 54 countries to temporarily ban or limit poultry and poultry product imports from the United States, according to news reports.

The first confirmed case was found in a backyard flock of mixed poultry in Douglas County, Ore., on Dec. 19. Subsequent cases quickly followed in two different backyard flocks in Benton County, Wash., Jan. 3 and 9. Two new cases in Clallam County, Wash., and Canyon County, Idaho, were discovered on Jan. 16, both in backyard flocks.

The first, and thus far only, case in a commercial flock appeared on Jan. 23 in a Stanislaus County, Calif., turkey flock. A flock of captive wild birds in both Washington and Idaho have also been identified.

Highly pathogenic strains are extremely infectious and fatal once established in a flock and have been known to affect humans. The two strains identified in the outbreak are H5N8 and H5N2. There have been no reports of the virus affecting humans and there is no immediate public health concern over the outbreak.

While backyard and outdoor poultry owners have been blamed for the outbreak, the virus’ source can be traced to migrating waterfowl in the Pacific Flyway, a reservoir for avian influenza viruses.

“There are four major flyways that migratory birds follow in the United States,” said Denise Derrer, Public Information director for the Indiana Board of Animal Health. “The Pacific Flyway is along the West Coast and there is another flyway separating us and poultry producers here in the Mississippi Flyway from the Pacific flyway.

“The greatest risk for exposure is in the outdoor flock. Commercial indoor flocks have the lowest exposure risk.” Derrer cautioned that tight biosecurity measures should always be maintained for both commercial and backyard poultry.

The H5N8 virus originated in Asia and spread rapidly through wild bird migratory flyways in 2014. The strain comingled with domestic avian influenza strains, creating new strains of mixed origins. Mutation into new viruses is common when two or more influenza strains meet.

According to Derrer, all countries are required to report outbreaks of any avian influenza to the World Organization for Animal Health (OIE). Countries use the information to block or ban imports based on information in the reports.

Joelle Hayden, USDA public affairs specialist, confirmed as of Jan. 30, 54 states have imposed import bans of live poultry and poultry products. Fifty of those countries have imposed temporary bans only from processors and hatcheries in the affected areas; however, four countries – South Korea, Russia, Thailand and China – have blocked imports from the entire United States.

“It’s not uncommon for countries to use an event like this as an excuse to impose trade barriers to keep out competition,” noted Derrer.

Clinical signs of avian influenza include lack of appetite and energy; decreased egg production; soft or misshapen shells; swollen eyelids, combs and wattles; purple discoloration of wattles, combs and legs; coughing and sneezing; diarrhea; and even sudden death with no clinical symptoms.

Any poultry flock owner in the United States, whether commercial or backyard, who suspects an avian flu outbreak, should contact the USDA at 866-536-7593. USDA employees will connect the flock owner with diagnostic labs that can confirm or deny suspected outbreaks.