As bird flu spreads in dairy cows, more surveillance is needed, health officials say

By Eleanor Laise

Milk needs better monitoring, WHO says after virus remnants are found in U.S. milk samples

Recent bird-flu outbreaks in dairy cows and other types of animals underscore the need for better surveillance of the virus across species, World Health Organization officials said Wednesday.

Now that it's clear that the virus can infect many different types of animals beyond poultry and wild birds, "what we really need globally is strong surveillance in different animal species," Maria Van Kerkhove, an infectious-disease epidemiologist at the WHO, said during a press conference held Wednesday by the global health organization. Milk and milk products also need better monitoring to ensure people are protected, Van Kerkhove said.

The WHO's comments come a day after the U.S. Food and Drug Administration said that remnants of the bird-flu virus had been found in pasteurized milk samples. "To date, we have seen nothing that would change our assessment that the commercial milk supply is safe," the FDA said, adding that the results of multiple studies would be available in the coming days and weeks.

The H5N1 bird-flu strain, which is widespread in wild birds globally, is causing outbreaks among U.S. dairy cows and has infected a U.S. dairy worker, according to the Centers for Disease Control and Prevention. Although the current public-health risk is "low" and no person-to-person spread has been detected, according to the CDC, the agency said it is carefully watching the situation and working with states to monitor people who have exposure to animals.

Although human infection with H5N1 is relatively rare, it's often deadly. Among nearly 900 human cases reported globally since 1997, the fatality rate is about 50%, according to the CDC. The agency has already made a candidate vaccine virus that could be used to create a bird-flu vaccine if needed, it said.

Although the detection of H5N1 in dairy cattle does not fundamentally change the WHO's risk assessment, it is "concerning," Van Kerkhove said. As the virus continues to circulate and mix with different animal species, she noted that "it has the potential to cause an epidemic outbreak and potentially become a virus that has that pandemic potential."

Research shows that pasteurization is very likely to inactivate heat-sensitive viruses such as H5N1 in milk from cows and other species, according to the FDA. During the pasteurization process, milk is heated to a specific temperature to kill potentially harmful bacteria and viruses. But given that the detection of the bird-flu strain in dairy cows is a new and evolving situation, no studies have been completed specifically examining how pasteurization affects avian-flu viruses in cow milk, the FDA said.

"Looking at this situation, we don't have enough information about the load of virus in raw milk" and how effective pasteurization might be, Dr. Moez Sanaa, head of the WHO's standards and scientific advice on food and nutrition unit, said at the press conference Wednesday. "There is some work to be done."

Climate change has likely contributed to the current H5N1 outbreaks in various species, Dr. Wenqing Zhang, an official with the WHO's global influenza program, said at the press conference. As the changing climate has impacted migratory birds' pathways and contributed to habitat loss, "it certainly plays a role in this type of unprecedented spread of the H5N1 virus," Zhang said.

-Eleanor Laise

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04-24-24 1255ET

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