As the US grapples with an ongoing bird flu outbreak in dairy cattle, the country’s health agencies are ramping up surveillance efforts and working to develop a vaccine if needed
By Grace Wade
26 April 2024
Dairy cows at a farm in the US
Shutterstock / Roman Melnyk
As a bird flu virus continues to spread among dairy cattle in the US, the country’s health agencies are actively preparing for the possibility of an outbreak in people.
“The risk [of bird flu] remains low at this time, but we continue to be in a strong readiness posture as new data becomes available,” said Vivien Dugan at the US Centers for Disease Control and Prevention (CDC) at a meeting of health officials on 25 April.
A top priority is tracking the virus’s spread. So far, the US Department of Agriculture (USDA) has confirmed H5N1, a subtype of the bird flu virus, in dairy cows on 34 farms across nine states, and in six cats on farms in three of those states.
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Genetic sequencing found that only one of the 260 samples from sick dairy cows so far has a mutation indicating H5N1 has adapted to infecting mammals, said Rosemary Sifford at the USDA during the meeting. However, this marker has been seen before in other sick mammals, and it didn’t impact the ability of the virus to transmit between mammals. Plus, the other 10 samples from the same herd where this one was collected didn’t have the same mutation.
“It very much remains an avian virus with no significant changes… In other words, it is not becoming a [cow] virus,” said Sifford.