Dairy cattle on farms in Kansas, Texas and possibly New Mexico have tested positive for avian influenza – the first time the virus has been found in cows.
"At this stage, there is no concern about the safety of the commercial milk supply or that this circumstance poses a risk to consumer health," the U.S. Department of Agriculture said earlier this week.
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Dr. Judith O'Donnell, director of Infection Control at Penn Presbyterian Medical Center, agreed.
"There should be no transmission through milk because milk through dairy cattle is taken to pasteurization and that would absolutely kill the virus," she said, adding that the virus is "...non-transmissible to a great degree from human to human."
Dead birds were found last week on two farms in Kansas and one in Texas, raising alarm. Unpasteurized milk samples from sick cattle tested positive Monday for highly pathogenic avian influenza, or HPAI. Wild birds seem to have introduced the virus to the cattle, according to the USDA.
Initial testing "has not found changes to the virus that would make it more transmissible to humans," according to the USDA.
Federal and state agencies are doing further testing, and also conducting viral genome sequencing, so that they can "better understand the situation, including characterization of the HPAI strains associated with these detections."
The news followed last week's report of a goat testing positive for HPAI on a Minnesota farm, the first time the virus had been detected in any kind of U.S. "ruminant," which includes goats, sheep, cattle and their relatives.
Bird flu first emerged in 1996 and has been decimating birds and poultry in many countries in Africa, Asia and Europe since 2020. The virus spread to North America in 2021.
"Avian influenza viruses normally spread among birds, but the increasing number of H5N1 avian influenza detections among mammals – which are biologically closer to humans than birds are – raises concern that the virus might adapt to infect humans more easily," the World Health Organization said last year. In addition, some mammals may act as mixing vessels for influenza viruses, leading to the emergence of new viruses that could be more harmful to animals and humans."
Still, virus detection in humans "remain very rare," the WHO said. Eight cases of avian influenza in humans have been reported since December 2021 worldwide.
Even people milking cows or coming into contact with milk of infected cattle would be at "relatively low risk" for contracting the virus, O'Donnell said.
Bird flu symptoms in people may include cough, headache, shortness of breath, fever or chills, fatigue, muscle or body aches. Infection in people have ranged in severity from no symptoms or mild illness to severe disease that resulted in death, according to the U.S. Centers for Disease Control and Prevention.
People can contract bird flu through prolonged and unprotected contact with infected birds or poultry – from people not wearing gloves or other personal protective gear and then touching their face, eyes, nose and mouth, the CDC says.
Something people should keep in mind is that "...backyard chickens are certainly at risk or potentially at risk for transmission from an avian flu," O'Donnell said. "People who keep chickens in their backyards need to be mindful of this disease."
The CDC recommends the following for people with backyard chickens believed to be infected with bird flu:
• Don't touch sick or dead birds, their feces or litter, or any surface or water source (for example, ponds, waterers, buckets, pans, troughs) that might be contaminated with their saliva, feces or any other bodily fluids without wearing personal protective equipment.
• Wear personal protective equipment when around sick or dead birds.
• As best as possible, during depopulation and while cleaning and disinfecting contaminated premises, avoid stirring up dust, bird waste, and feathers to prevent the virus from dispersing into the air.
• Once bird flu infection is confirmed within a flock and premises, the USDA's Animal Plant Health Inspection Service recommends that backyard owners continue to wear PPE when in contaminated areas until there are no longer infected birds, eggs, feces or contaminated litter on the property. The recommendation to wear PPE when in contaminated areas (primary poultry housing: coops, runs, barns, etc.) depends on whether a 150-day fallow is used for virus elimination after flock depopulation.