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Possible evidence of windborne H5N1 viral infections in chickens

A team of government veterinarians with the State Veterinary Institute Prague in the Czech Republic has found possible evidence of windborne H5N1 infections in chickens. In their paper on the bioRxiv preprint server, the group describes how chickens in a closed environment became infected with the H5N1 virus despite no contact with other chickens, wild birds, or their feces, leaving the wind as the only likely source.

The H5N1 virus is responsible for a worldwide avian flu pandemic in chickens. The virus has been determined to be a subtype of the influenza A virus and was first observed in China in 1996. Since then, it has infected birds across the world, with epidemics rising and falling in different countries at different times. Because of a policy in the U.S. requiring chicken farmers to kill all their birds if even one is infected, the chicken population has decreased dramatically, resulting in skyrocketing egg prices.

Prior research has suggested that birds infect one another via the transfer of saliva, mucus or contact with feces. Infections between other types of animals have been seen due to the transfer of bodily fluids such as saliva, milk or even blood. Once an infection occurs in a single location, such as a chicken farm, it can spread rapidly. Research has also suggested that infections at sites such as chicken farms most likely occur due to wild birds dropping feces near the chickens. In this new effort, the research team found an incident where a chicken farm was infected without any known outside source, suggesting the wind carried the virus.

In their case, the veterinarians were conducting research on a highly secure chicken research farm—the birds there were not allowed out of their cages or barns. The water came from a secure well and was filtered to remove pathogens. The barns have large fans that create a one-way airflow, and the entire facility is surrounded by a highly secure fence.

Also, no employees came into contact with any other birds when not on duty. Still, the farm experienced an infection. The veterinarians suggest the only possibility left is that the virus was carried aloft by the wind and wafted into the barn, settling on the captive birds.

No evidence of the virus traveling via the wind has been found. The evidence is circumstantial, but the team suggests the virus could have hitched a ride on a bit of dust from hay exposed to wild bird excrement.