Avian flu infects Colorado dairy herd

Current public health risk still low despite rapid spread, health authorities say

Colorado became the ninth state in the US to report a dairy herd infected with bird flu as federal lawmakers urged the Biden administration to further contain the virus’ spread and tests of milk suggested the outbreak is more widespread than previously thought.

The US Agriculture Department (USDA) confirmed milking cows in Colorado tested positive, after earlier infections in Texas, Kansas, Michigan, Ohio and New Mexico.

One person, a Texas farm worker, has been confirmed to have bird flu and suffered conjunctivitis in the current outbreak following exposure to dairy cows.

Both the Centres for Disease Control and Prevention and the World Health Organisation said on Friday the current overall public health risk is low but is higher for those with exposure to infected animals.

Congress members’ push for a stronger response added pressure on federal agriculture and health authorities still seeking to confirm how the H5N1 virus is spreading and its potential risks to people, one month after the first detection in a Texas dairy herd. An analysis of USDA data by a University of Arizona scientist offers new evidence that the first known H5N1 outbreak in dairy cattle is more far-reaching than the 34 herds in nine states that have officially tested positive.

The recent spread of bird flu and the detection of H5N1 genetic materials in milk have increased some calls for action.

The virus in the human case is significantly different from the bird flu virus samples taken from infected cattle that were made public by government officials last weekend, said Dr Michael Worobey, an evolutionary biologist from the University of Arizona.

The difference between the genetic sequences of the worker’s virus and the 239 other samples provided indicate that “this was a very longstanding, widespread epidemic”, he said.

“I think the sequences out there probably aren’t representative of everything that’s circulating,” said Dr Richard Webby, a virologist at St Jude’s Children’s Research Hospital in Memphis.

One in five commercial milk samples tested in a nationwide survey contained particles of the H5N1 virus, the US Food and Drug Administration said late on Thursday.

The agency said there is no reason to believe the virus found in milk poses a risk to human health.

“This says this virus has largely saturated dairy cattle throughout the country,” said Dr Michael Osterholm, an infectious disease expert at the University of Minnesota.

Starting Monday, the USDA will require dairy cows to test negative for bird flu before they are moved across state lines. — Reuters