H5N1 avian flu now affecting more than two thirds of states

Heads of domestic geese
Heads of domestic geese

OliBac / Flickr cc

With highly pathogenic H5N1 avian flu now in Washington state and in Oregon poultry for the first time, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) confirms that the disease has now affected 34 US states and led to the demise of 37.55 million poultry.

Officials also confirmed new poultry outbreaks in Wisconsin, Michigan, Minnesota, Iowa, and Montana, as well as more positive tests in wild birds. And the World Health Organization (WHO) provided updates on human avian flu cases in Colorado and China.

Washington, Oregon outbreaks in backyard flocks

Animal health officials in Washington reported outbreaks in backyard flocks late last week.

In a May 6 news release, the Washington State Department of Agriculture (WSDA) said flock owners in Pacific County in the state's southwest reported sick and dying birds, and samples taken on May 4 tested positive for the H5N1 strain on May 5 in state and federal labs. APHIS said the flock contained 50 birds.

Amber Itle, DVM, state veterinarian, quarantined the premises and ordered the remaining birds culled to contain the outbreak.

This is the first detection of the virus in Washington state in 2022. There have been no detections in commercial poultry in the state.

"We have a vigorous response plan, but this development demonstrates how important good biosecurity can be, especially for backyard bird owners," Itle said. "We have not diagnosed the virus anywhere else in our domestic poultry population, but the presence of the virus in migratory waterfowl is a risk to backyard poultry. One step owners should take is preventing contact between their birds and wild birds."

The WSDA confirmed a second outbreak, involving 80 backyard poultry in Spokane County in the east, on May 7. The agency said the flock is a mix of geese, chickens, ducks, and guinea fowl.

A veterinarian submitted for testing a dead goose that had exhibited unusual behavior, including walking abnormally, shaking its head, not moving, and exhibiting a lack of fear of humans. The owner reported other sick birds and deaths. Lab tests confirmed H5N1 avian flu on May 7.

Itle said poultry owners should eliminate access to ponds or standing water on their property and keep different poultry species like ducks and geese penned separately from chickens and turkeys.

The affected backyard flock in Oregon is in Linn County in the northwest and contained 180 poultry. The Oregon Department of Agriculture (ODA) said in a May 6 news release that APHIS confirmed H5N1 highly pathogenic avian influenza (HPAI) on that day.

"We knew HPAI was coming our way after a bald eagle in British Columbia tested positive in early March," said Ryan Scholz, DVM, MPH, state veterinarian. "Since that detection, we have been hard at work communicating with our commercial poultry producers, veterinarians, and the public on how they can protect their flocks. Now more than ever, all bird owners must practice good biosecurity, prevent contact between their birds and wild birds, and report sick birds."

In a news release, the USDA said the Washington and Oregon outbreaks were confirmed via testing at the APHIS National Veterinary Services Laboratories in Ames, Iowa.

Wisconsin turkey farm hit

Tests on May 7 confirmed HPAI on a turkey farm in Barron County, Wisconsin, APHIS said. The farm is in the northwestern part of the state. Wisconsin also had an outbreak in a backyard flock of 30 birds in nearby Pierce County.

Other Midwestern outbreaks involving backyard flocks include an outbreak on an Oakland County, Michigan, farm housing 50 birds; an outbreak among a 10-bird flock in Anoka County, Minnesota; and an event involving 50 poultry in Bremer County, Iowa.

The affected backyard holding in Montana is in Fergus County in the central part of the state and houses 20 birds.

The USDA, on its wild bird avian flu detection page, notes 29 more positive tests, mostly in waterfowl and raptors, raising the total to 1,035. The new detections are mainly from North Dakota, with more crow deaths, and Wisconsin. A loon found dead in Minnesota also tested positive.

More details on human cases

The WHO updates involve the first-ever US human H5N1 avian flu case, which was first reported on Apr 28, and the world's first known human case involving the H3N8 strain, which China reported on Apr 26. The latter WHO update clarifies the severity of the infection in a young boy.

In a May 6 news release, the WHO said the Colorado man, reported earlier as a state prison inmate, developed fatigue on Apr 20 while slaughtering poultry at commercial farm in Colorado that had been confirmed as having an H5N1 outbreak. His sample was collected the same day and was confirmed by polymerase chain reaction (PCR) testing on Apr 27.

The man was isolated and treated with antiviral medication on Apr 26. He did not report other symptoms, was not hospitalized, and has now recovered, the WHO said.

In a news release today, the WHO noted that a 4-year-old boy from Henan province in China developed fever, cough, and shortness of breath on Apr 5 and was admitted to the hospital in critical condition on Apr 10 after he developed severe pneumonia with respiratory failure. The boy received antiviral drugs in the intensive care unit.

Chinese officials confirmed H3N8 avian flu on Apr 24. The WHO said no further cases have been detected among the boy's close contacts.

Before falling ill, the boy had eaten chickens that were kept in the family's backyard but did not have direct exposure to them before he got sick. Officials continue to conduct epidemiologic and virologic investigations.

The WHO did not specify the boy's current status.

The agency concludes, "Currently, limited available epidemiologic and virologic information suggests that this avian influenza A(H3N8) virus has not acquired the ability of sustained transmission among humans. Therefore, the risk at the national, regional and international level of disease spread is assessed as low."

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