Expert describes devastating effects of bird flu as traces of virus are found in fifth of US milk

One in five retail samples of commercial milk has traces of bird flu, the Food and Drug Administration (FDA) said this week.

The H5N1 strain of avian flu was first detected in Texas herds in March — and it has since been found in more than three dozen herds in nine states, according to the US Department of Agriculture. The ninth state, Colorado, detected its first known case on Friday.

“The agency continues to analyze this information; however, the initial results show about 1 in 5 of the retail samples tested are ... positive ... with a greater proportion of positive results coming from milk in areas with infected herds,” the FDA said.

With the rise in bird flu and its presence on six continents, the “worst case” for livestock is near, according to Maurice Pitesky, a specialist at the University of California, Davis, School of Veterinary Medicine.

“[The virus] has demonstrated an ability to move into dairy cows, and while it doesn't cause mortality it causes a decrease in milk production, which has economic impacts,” Mr Pitesky told The Independent. “This ultimately will affect the ability to produce fluid milk and all the things that are associated with it.”

Egg producers are also on high alert after chickens tested positive for the virus in Texas and Michigan. Officials have killed millions of birds. But while the FDA maintains the risk of human infection is still low, if the virus continues to spread, it could also have significant ecological and economic consequences.

“There’s a wildlife scenario that’s also devastating,” Mr Pitesky said. “The virus is affecting sea lions and elephant seals and albatross and all these other things that are seeing their populations being devastated.”

The only recent human case of H5N1 was in a US dairy worker, according to the Centers for Disease Control (CDC). The worker’s only symptom was eye redness consistent with conjunctivitis, the CDC reported. The worker is only the second known person in the US to test positive for the virus.

More dairy workers could contract the disease if it continues to spread, Mr Pitesky said.

“Farmworkers are working in these environments with lots of dairy cows that are affected,” he told The Independent. “They're the frontline of surveillance and also the frontline of people that are that are potentially most susceptible to getting sick.”

Now, dairy cattle moving between states have to be tested for the virus to control the growing outbreak. Every lactating cow must now be tested and receive a negative result before moving across state lines. The herds known to carry the virus are located in Idaho, Kansas, Michigan, New Mexico, North Carolina, Ohio, Texas and South Dakota.

Meanwhile, US lawmakers are urging the Biden administration to take swift action.

Democratic Senator Tammy Baldwin, who represents Wisconsin, a significant dairy state, wrote a letter to the USDA on Thursday urging them to allocate further resources to fighting the virus.

“It is imperative the agency quickly deploy additional resources in states that have the opportunity to prevent the disease from entering herds within their borders by working directly with farmers on improving their biosecurity options,” Ms Baldwin wrote.

Health agencies and experts are emphasising that dairy products are still safe to consume.

“To date, the retail milk studies have shown no results that would change our assessment that the commercial milk supply is safe,” the FDA said.

To stay safe, the FDA says consumers should drink pasteurised milk, as the process eliminates pathogens to a level that does not pose a risk to human health.

“This is the millionth reason to drink pasteurized milk,” Mr Pitesky told The Independent. “I'd be very concerned for folks that drink raw milk, I think that's a real risk.”

Michael Hansen, senior scientist with Consumer Reports, said there is no individual risk to consumers who drink pasteurised milk — but that this outbreak does pose a public health concern.

“Where there is an issue is with public health,” Dr Hansen told The Inependent. “Should public health people be concerned? Absolutely. Because a worst case scenario is so bad — and that's what public health does.”

“So something can be a public health concern, but from the individual level, they don't necessarily have to freak out about it,” Dr Hansen continued.

The symptoms of bird flu in humans range from no symptoms to severe symptoms, according to the CDC. These can include fever, fatigue, and difficulty breathing. Less common symptoms include diarrhoea, nausea, vomiting, or seizures, the CDC said. Human-to-human transmission is also rare.

Patients outside of the US have died from the virus, the CDC reports.