SALEM, Ohio -- Bird flu is back in poultry in Pennsylvania. The Pennsylvania Department of Agriculture on Jan. 27 confirmed a case of highly pathogenic avian influenza in a 50,000-bird layer chicken flock in Lehigh County.
The department quarantined the farm and all commercial poultry facilities within 10 kilometers of the infected flock, restricting the movement of poultry products in that radius.
Preliminary samples indicated the presence of the H5N1 bird flu when tested in a PA Animal Diagnostic Laboratory System lab. Samples have been shipped to a USDA National Veterinary Services Laboratory for confirmation. All the birds at the affected farm will be depopulated to prevent the spreading of the virus.
The last detection of HPAI in domestic birds in Pennsylvania was in a backyard flock with 20 birds in October 2024 in Venango County. This detection is the first confirmed in commercial poultry in Pennsylvania since February 2024.
Pennsylvania has been on high alert since the beginning of the outbreak of HPAI in the U.S. in 2022. An outbreak from April 2022 to March 2023 caused the loss of more than 4 million domestic birds in Pennsylvania, primarily in the south-central part of the state.
Since the bird flu was found in dairy cattle in March 2024, Pennsylvania has been a national leader in testing milk and dairy cattle, prohibiting lactating dairy cattle from infected farms in other states from transport to Pennsylvania.
Per the department of agriculture's quarantine order, dairy farms within 3 kilometers of the infected flock must submit weekly bulk tank or in-line milk samples representing the entire milking herd until the control area is closed.
The Lehigh Valley in eastern Pennsylvania is the epicenter of the state's latest bird flu outbreak. The Pennsylvania Game Commission initially called attention to 200 snow geese found dead at two sites -- one in Northampton County and one in Lehigh County -- in a Jan. 2 press release. It was later reported that more than 5,000 snow geese died from bird flu in the Lehigh Valley.
Wild birds, especially waterfowl, are reservoirs for bird flu and spread it in their feces. The virus enters new areas and impacts vulnerable domestic poultry populations during migration. The H5N1 bird flu outbreak has caused the loss of more than 140 million domestic poultry in the U.S.
The outbreak of H5N1 also has expanded to mammals, including domestic cats, foxes, polar bears, raccoons, marine animals such as dolphins and seals and livestock like dairy cattle and goats.
While there have been human infections of HPAI, mainly in workers in close contact with infected poultry and dairy cattle, according to the U.S. Centers for Disease Control and Prevention, avian influenza presents very low risk to human health.
However, the introduction of H5N1 infection in many new species other than birds concerns researchers because of the viruses' ability to both mutate and reassort, which could eventually lead to more severe human infection. The H5N9 bird flu was recently discovered at a commercial duck farm in California.