Bird flu has been spreading undetected in cows and vets, according to US CDC report

Three cow veterinarians have tested positive for bird flu antibodies in the United States, according to a new study that suggests not all virus infections are being detected.

The current outbreak of avian influenza (H5N1) in dairy cows in the US was first reported in March 2024 and has now spread to 968 dairy herds, according to the Centers for Disease Control and Prevention (CDC).

There have been 68 confirmed cases in humans and one death in the US but no reported spread between people.

In a newly released CDC study, 150 cow veterinarians in the US and Canada had their blood tested for avian influenza antibodies to determine if they had a recent bird flu infection.

Out of the three US veterinarians who were found to have antibodies for the virus, none of them reported previous symptoms of influenza or conjunctivitis, which is often a symptom of human bird flu infections. 

This suggests that monitoring only symptomatic exposed workers may “underestimate human infection,” the CDC said.

None of the veterinarians had worked with cattle that had a suspected bird flu infection, although one person had worked with infected poultry. One of the practitioners had provided care to cows in states without reported bird flu infections in cows or humans.

This means that dairy cattle could be infected with bird flu in states where the virus has not yet been identified in cows.

Rowland Kao, a professor of veterinary epidemiology and data science at the University of Edinburgh in the UK, told Euronews Health that the findings were “not that surprising” but it does mean it may be harder to “completely eradicate” the outbreak. “Every time a human gets infected, there’s a chance of either a direct evolution of the virus or a recombination with