Scientists criticize federal response to bird flu outbreaks on dairy farms

Officials have shared little information, saying the outbreak is limited. But asymptomatic cows in North Carolina changed the assessment.

In the month since federal authorities announced an outbreak of bird flu in dairy farms, they have repeatedly reassured the public that the wave of infections is not impacting the country's food or dairy supply and poses little risk to the public.

Yet the outbreak in cows could be more serious than initially thought. In an obscure online update this week, the Agriculture Ministry said there is now evidence that the virus is spreading between cows and from cows to poultry.

North Carolina officials have detected bird flu infections in a herd of cattle without symptoms, the New York Times has learned — information from the U.S.D.A. has not shared publicly. The findings suggest that infections may be more widespread than previously thought.

It's not clear whether there are asymptomatic animals elsewhere, because the U.S.D.A. does not require farms to test cattle for infection. It reimbursed farmers for testing, but only for 20 cows per farm that were visibly sick. This week, the department announced it would begin reimbursing farms that test cows without symptoms.

Federal officials have shared limited genetic information about the virus with scientists and officials from other countries. , which is important for understanding how the virus might evolve as it spreads.

They do not actively monitor infections in pigs, which are hosts known to be effective for the evolution of influenza viruses, and which are often kept near livestock. And officials said they had "no concerns" about the safety of the milk, despite the lack of hard data.

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