Federal regulators said Tuesday that samples of pasteurized milk from across the country tested positive for inactive remnants of the avian flu virus that infects dairy cows.
The viral fragments do not pose a threat to consumers, officials said. “So far, we have not seen anything that would change our assessment that the commercial milk supply is safe,” the Food and Drug Administration said in a statement.
Over the past month, an avian flu virus known as H5N1 has been detected in more than 30 dairy herds across eight states. The virus is also known to have infected a farm worker, whose only symptom was conjunctivitis.
Scientists have criticized the federal response, saying the Agriculture Department has been too slow to share important data and has not adequately tested cattle for infection.
Finding viral fragments in milk from the commercial supply chain is not ideal, but the genetic material poses little risk to consumers who drink the milk, said David O’Connor, a virologist at the University of Wisconsin-Madison.
“The risk of being infected by milk containing viral fragments should be zero,” he said. “Genetic material cannot replicate itself.”
Authorities did not say how many samples of pasteurized milk tested positive for the presence of viral fragments or where those samples came from. These are key questions, experts say.
If the fragments are present in many samples throughout the commercial milk supply, this suggests that the outbreak is likely much more widespread than has been reported.
Last week, The New York Times reported that the virus had also been detected in a herd of North Carolina dairy cows that showed no symptoms of illness.
“The problem in dairy cows could be much bigger than we think,” Dr O’Connor said. “That would be our concern – not that the milk itself poses a risk. »
Federal officials have repeatedly reassured consumers that the commercial milk supply is safe, emphasizing that dairy producers are required to keep milk from sick animals out of the human food supply.
And almost all milk produced on American farms is pasteurized, a process designed to kill pathogens with heat. Pasteurization should also inactivate flu viruses, which are known to be fragile and sensitive to heat, experts say. Only recently has the FDA tested the effectiveness of pasteurization on H5N1.
The discovery of viral fragments in milk has raised serious concerns at the White House about how to avoid raising unwarranted alarm over the dairy supply, according to people familiar with the internal deliberations who were not authorized to speak about it publicly.
Federal officials are expected to revisit these findings at a press briefing in the coming days.
This developing story will be updated.
