For the first time, highly pathogenic avian influenza (HPAI), commonly called bird flu, has been reported in cows. The US Department of Agriculture (USDA) recently confirmed that dairy cows in five states have tested positive for the HPAI subtype H5N1, a virus that has caused the deaths of over 130 million birds so far. 

The major concern is that this outbreak suggests the virus might have mutated to jump to cattle more easily, and cattle are defenseless against this. To make matters even worse, a human has now caught bird flu from a cow. So, what should and shouldn’t we be concerned about, and what is the current situation?

An unexpected case

A subtype of the H5N1 virus known as clade 2.3.4.4b has been ravaging bird populations worldwide for around two years. In a new twist, the virus seems to have made its way to cattle, and from cattle it can apparently also spread to humans.

According to a report from Texas, a person in contact with infected animals was tested after experiencing eye inflammation. Flu testing confirmed the presence of the H5N1 virus. Fortunately, this was the only known symptom, and the patient is receiving treatment.

“[The] infection in someone with exposure to sick animals is not surprising, but [is] concerning,” said Dr Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health in the US. Writing on X (formerly Twitter), Nuzzo added that added that the case is “notable” as the expanding “geographic and species spread increases concerns about virus’ future potential to infect humans”.

Currently, the virus has been detected in cows at various dairy farms in Texas, Michigan, Kansas, New Mexico, and Idaho. The real spread could be far greater as careful monitoring is not in place. However, no livestock death has been reported to date because of bird flu. 

Most of the infected cows were older in age, and many of them recovered after isolation. What’s particularly concerning is that the virus seems to also be spreading to other species. About a week ago, the USDA also identified the first case in a goat in Minnesota. This suggests that H5N1 is spreading quickly from birds to other animals. 

“However, initial testing has not found changes to the virus that would make it more transmissible to humans. While cases among humans in direct contact with infected animals are possible, this indicates that the current risk to the public remains low,” the USDA stated.

Symptoms and causes of bird flu in cattle

Avian influenza severely affects the respiratory organs and digestive systems of birds, causing high mortality in poultry. Even the birds that survive the virus, are culled to prevent the virus from spreading further.

In cattle, the disease typically leads to milder symptoms. In fact, the only symptoms infected dairy cows show are fever, reduced milk production, and low appetite. Since these animals also recover quickly, there is no need to cull them, according to the current USDA recommendations.

It is suspected that H5N1 is transmitted to cows either from infected or dead poultry, or through the oral secretions or excreta of wild or farm birds. Moreover, the virus has probably reached a state where it is spreading from one cow to another. 

For instance, recently, National Veterinary Services Laboratories (NVSL) revealed that a few days after a dairy farm in Michigan received cows from Texas, their livestock developed the HPAI infection. 

“Spread of symptoms among the Michigan herd also indicates that HPAI transmission between cattle cannot be ruled out; USDA and partners continue to monitor this closely and have advised veterinarians and producers to practice good biosecurity, test animals before necessary movements, minimize animal movements, and isolate sick cattle from the herd,” the USDA said. 

The agency also recommends heating milk from infected cows before feeding their calves to prevent infection in the latter. 

Should you stop using dairy products?

Some farms in the US have had to “divert or destroy” milk produced by the infected cows. They are only allowed to process and sell milk obtained from healthy livestock. Moreover, milk undergoes a process called pasteurization before it reaches your home.

Pasteurization involves rapid heating and cooling of milk and other food products. This process kills all the harmful microorganisms (including viruses) present and extends the shelf life of perishable edibles.

“There continues to be no concern about the safety of the commercial milk supply because pasteurization is required for any milk entering interstate commerce for human consumption, and it has continually proven to inactivate bacteria and viruses, like influenza, in milk,” the USDA said.

Therefore, there is currently no need to discard milk and other dairy products. 

However, if you are someone who has the habit of consuming raw unpasteurized milk, you’re at risk. The authorities have no idea whether raw milk may carry the virus. Both the USDA and the Food and Drug Administration (FDA) warn against selling or drinking raw milk.

“The FDA recommends that industry does not manufacture or sell raw milk or raw/unpasteurized milk cheese products made with milk from cows showing symptoms of illness, including those infected with avian influenza or exposed to those infected with avian influenza,” the USDA stated.

When it comes to the risk of HPAI infection from consuming infected beef, the USDA claims that cooked cattle meat is safe to eat.

“USDA is confident that the meat supply is safe. As always, we encourage consumers to properly handle raw meats and to cook to a safe internal temperature. Cooking to a safe internal temperature kills bacteria and viruses, like influenza, in meat,” the USDA notes.

However, the agency and its partners are constantly monitoring the situation and posting updates. They have also released a document addressing FAQs related to the infection and other resources to help cattle owners.

Hopefully, all these efforts and information will be enough to keep this flu under control.