Cases of bird flu among animals continue to rise as US officials warn about the role of humans in spreading the virus.
There are now 102 herds in the US with H5N1 cases, although given the prevalence of inactivated virus in commercially available pasteurized milk, experts believe the actual number may be even higher.
Poultry farms have reported cases likely linked to dairy farms, suggesting the virus may be passing from cows to birds. As of 2022, nearly 97 million domestic birds in the US have been affected by highly pathogenic influenza.
Although officials believe this outbreak was originally sparked by a single introduction of migratory birds to cows – for example through feed contaminated with bird feces – late last year, genomic analyzes now suggest the disease is being spread between animals and farms through human activity. report The United States Department of Agriculture (USDA) announced this on Thursday.
The report, which focused on cases in Michigan, found that transmission is likely to occur when workers, cows, vehicles and equipment move to multiple farms.
Of employees at dairy companies with outbreaks, one in five employees works at other dairy companies and 7% also work at poultry farms. This is in addition to the veterinarians, nutritionists and transporters who regularly visit several farms.
Three in five Michigan dairies with outbreaks use shared vehicles to transport cows, but only 12% clean the vehicles first. All but one of the affected dairies are members of the same milk cooperatives.
The results correspond to one second report also released Thursday by the USDA, showing that about a third of workers at U.S. dairies with outbreaks also work on other farms with livestock — usually dairy farms, but sometimes pigs and poultry.
More than half of affected U.S. dairy farms share trucks and trailers to transport cows, and more than half of those who share vehicles do not clean them first, the report said.
“Biosecurity is the key to prevention,” Kammy Johnson, a veterinary epidemiologist with the USDA’s Animal and Plant Health Inspection Service, told reporters Thursday. That means disinfecting everything that moves from farm to farm – transportation, clothing, equipment – and reducing the chance that infected animals or people will pass on the virus.
It’s not clear whether the outbreak will continue to gain momentum, officials said, but they to expect to find more cases in cows.
And as the virus continues to evolve, it may become a greater threat to humans, according to a recent publication report by the US Centers for Disease Control and Prevention (CDC). Officials expect more cases of bird flu among humans to occur as the outbreak continues, the report said.
“The more infections there are among cows, the greater the risk of infections occurring among humans,” Dr. Nirav Shah, deputy director of the CDC, told reporters on Thursday.
“The fact that it’s in 20% of our milk production should be alarming to everyone because that means it’s already out there,” said Xavier Becerra, secretary of the Department of Health and Human Services. said last week. “If it starts jumping, we really have to worry.”
Yet testing has lagged behind, in a situation reminiscent of the Covid-19 pandemic.
The only authorized test for H5N1 in humans comes from the CDC and is only available to people who have symptoms and a history of close contact with infected animals or other people. So far there have only been 45 tests carried out this year.
Yet there have been reports of workers with positive influenza A tests that have not been sequenced for H5N1, as well as possible missed caseslike the farm workers and a local maternity nurse who reported flu-like symptoms near the first confirmed human case this year in Texas.
Providers can now be hesitant to test for flu even if a patient has respiratory symptoms, since flu season has ended and so insurance companies may not pay for the tests.
The USDA required Lactating dairy cows must be tested before crossing state lines. The federal government does not have the authority to require widespread testing of animals or humans, meaning these efforts largely fall to state and local entities.
In Wisconsin, for example, where no infections in cows have yet been reported, farmers are now doing so required to test cows before taking them to fairs and exhibitions.
In any case, cows have died five states – South Dakota, Michigan, Colorado, Ohio and Texas – because they did not recover or developed secondary infections after testing positive for H5N1. The majority of infected cows recover, but these deaths indicate the potential financial burden of an uncontrolled outbreak.
Barn cats and mice have that too tested positive for H1N1, concerns have arisen that the animals could spread the virus in communities outside the farms.