At the end of March, The United States Department of Agriculture (USDA) announced that it had detected cases of avian flu in dairy cattle. Initially discovered on dairy farms in Texas, Kansas and New Mexico, there are now 36 confirmed. Outbreaks in dairy herds in nine states..
Although the H5N1 virus circulates widely among wild birds, it is now circulating among dairy cattle in the United States. The USDA has confirmed transmission between cows in the same herd, from cows to birds, and between different dairy cattle herds.
But the reported outbreaks are likely to greatly underestimate the true spread of the virus, says James Wood, head of veterinary medicine at the University of Cambridge. “There is likely to be a considerable amount of underreporting and underdiagnosis,” he says.
Testing by the Food and Drug Administration (FDA) on retail milk samples could give some indication of how widespread the virus is. The agency found viral fragments in one in five commercial milk samples, although this virus had been inactivated through pasteurization, so it was not infectious.
So far there is only one confirmed human infection in the outbreak: someone in Texas who had close contact with dairy cattle. Your only reported symptom it was conjunctivitis, and the individual was told to isolate and take an antiviral flu medication. But anecdotal reports of illnesses on dairy farms hint that infections among humans may be more widespread than official. the data suggests. Although human infections have tended to be rare, the virus is dangerous: just over half of the human cases recorded by the World Health Organization in the past two decades. they have been fatal.
Dairy workers are most at risk for possible infection in the current outbreak, but understanding the extent of any infection is extremely complicated, says James Lawler, a professor of infectious diseases at the University of Nebraska Medical Center. More than half of U.S. dairy workers are immigrantsand many from them They are undocumented.
These undocumented workers are unlikely to want to put themselves at risk by coming to get tested, Lawler says. “There is an inherent disincentive that many of the workers, due to their status as undocumented immigrants, do not raise their hands.” The result, Lawler says, is that scientists are finding it difficult to trace any possible spread of the virus through humans.
Another problem is incentivizing dairy farm owners to report when their animals appear sick. The USDA Animal and Plant Health Inspection Service provides payments specifically to poultry farmers who have to cull their livestock due to avian flu infections. Dairy farmers are not compensated for reporting infections, which incentivizes farmers to remain silent, increasing the risk that outbreaks get out of control and spread to other livestock or farm workers.
This presents a major problem in tracking the spread of the disease. “From a producer’s perspective, how will it benefit you to share or even test and understand if there is a virus circulating in your herd?” Lawler says.