Study gives clues about spread of H5N1 bird flu in cows and how to stop it

• Unpasteurized milk can spread the H5N1 bird flu virus between cows and humans.
• A new study has shown that the virus can survive in raw milk found in milking equipment for more than an hour.
• Better cleaning of milking equipment and worker protective gear could limit the spread of the virus.

Contaminated milk could spread H5N1 avian flu between dairy cattle, contributing to a major outbreak in 12 US states. This may also be how humans become infected.

A new study shows that the virus can survive for more than an hour in raw (unpasteurized) milk left on the surface of materials used in dairy cattle milking equipment.

It’s a clue to the mystery of how the virus spread so quickly among U.S. dairy cattle, infecting more than 130 herds in Idaho, Michigan, Colorado, Texas and more.

The cattle outbreak has scientists increasingly concerned because the H5N1 virus could mutate enough to cause an outbreak in humans. The more the virus spreads among cattle, the more opportunities it has to mutate.

Since April, three farmworkers have tested positive for the virus, but experts have found no evidence of human-to-human spread.

Understanding how the virus spreads between cattle is essential to controlling the outbreak and preventing further human infections.

“We need to know which dairy herds are infected, with which virus strains, how the infection spreads between farms and how often dairy farm workers and others are exposed,” said Christopher Dye, an expert in infectious diseases and professor at the University of Oxford, to Business Insider in an email.

According to the FDA, pasteurized milk purchased in supermarkets is still safe. However, raw milk could be an infectious agent.

How to help stop the spread of H5N1 bird flu

Authorities already knew that the H5N1 virus spread from farm to farm through the movement of cows, equipment and people, and that the virus concentrated in the udders and milk of sick cows.

“This means that even a small drop of milk can spread disease,” Agriculture Secretary Tom Vilsack wrote in a June 21 editorial.

Indeed, the new study found that the H5N1 virus remained infectious in raw milk for more than an hour on inflatable liners made of stainless steel and rubber, materials used in milking equipment.

The research was published Monday in the journal Emerging Infectious Diseases.

Milk may not be the only route of transmission. Cows could infect each other by licking each other or sticking their heads in feed, for example, says Meghan Davis, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health and a former dairy veterinarian.

However, the study suggests that cleaning milking equipment between cows and equipping workers with protective gear could help prevent the spread.

“Workers are usually down, in a recessed area, and the udder is at face height,” Davis told BI.

This is for their comfort and ability to work at milking for long periods of time, but it puts them at risk of milk splashing on their face.

Protective glasses and face shields may be helpful. For the moment, this is not a common practice in dairy production workshops.

Other types of protective gear, like N95 masks, can be difficult to implement on dairy farms because of the hot and humid conditions, Davis said. That can make heavy protective gear incredibly uncomfortable or even put workers at increased risk of heat-related illness.

As for cleaning milking equipment, she added, “there are cleaning processes, but the level of disinfection you need to inactivate the virus generally goes beyond what might be normal practice.” .

The ideal cleaning process may differ from farm to farm depending on transmission dynamics, the vulnerability of different cows and the degree of capriciousness of the animals.

Long breaks between milkings to clean can affect the amount of milk a cow produces and even be harmful to the animal, Davis said. It can also result in longer exposure periods for workers because it takes longer to milk a line of cows.

On the consumer side of the dairy industry, the study also serves as further proof that no one should drink raw (unpasteurized) milk.