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Chasing the avian flu virus: Research shows airborne transmission is a possibility

Scientists do not yet know whether spring winds carried the highly pathogenic avian influenza into barns and infected turkey or egg-laying flocks. But they now consider airborne transmission a possibility in some of the cases of infected barns, a...

Scientists do not yet know whether spring winds carried the highly pathogenic avian influenza into barns and infected turkey or egg-laying flocks.

But they now consider airborne transmission a possibility in some of the cases of infected barns, according to the United States Department of Agriculture. It recently reported that "a preliminary analysis of wind data showed a relationship between sustained high winds and an increase in the number of infected farms approximately five days later."

An important part of the research showing that airborne transmission is a possibility was undertaken by a team including Dr. Montserrat Torremorell, D.V.M. She is an animal health expert with the University of Minnesota. Team members chased the virus at infected farms in Minnesota, Iowa and Nebraska during much of April and May.

"Like a bit of witch hunting,'' said Torremorell when describing the research recently to the Tribune. They needed to capture genetic material of the virus in the air in barns, outside of barns, and on the wide open landscapes surrounding them.

Torremorell and the team were able to show that the H5N2 virus is capable of becoming airborne and leaving the barns with infected birds.

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"Viruses don't have wings,'' Dr. Torremorell said. She said the influenza virus becomes airborne by hitching rides on tiny, invisible particles of dust, fecal matter, or feed commonly present in turkey and egg-laying facilities.

Samples of air taken in barns with infected flocks tested positive for the virus, she said.

The crew also took their equipment downwind of the infected barns and also collected air samples that tested positive for the genetic material of the virus. They showed that the ventilation systems of infected barns were exhausting the virus to the outside.

Just how far the winds can carry the virus is not known. Once exhausted from a barn, the virus is dispersed into an ocean of air. The farthest the team was able to find genetic material from an infected barn was about three-quarters of a mile, Torremorell said.

The farther you go, the more difficult it is to detect the virus.

And, the virus is considered fragile. Once outside, ultraviolet light and other environmental factors can break it down.

More research is needed to determine whether the winds are responsible for actually transmitting the disease from one barn to another, Torremorell said.

"Our research cannot answer whether the neighboring farms are infected because of the air. We can just say if air can be a possibility,'' she said. In scientific terms, the research demonstrated a "proof of concept,'' that airborne transmission is possible.

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"If the virus comes back in the fall, we need to do more research to get a much better quantification of the risk of the air versus other factors,'' she said.

In its report, the USDA stated that there are likely several ways the virus could be transmitted. They include lapses in biosecurity practices and environmental factors.

Work by the USDA Animal and Plant Health Inspection Service found cases where equipment had been shared between infected and non-infected farms; employees moved from infected to non-infected farms; cases of improper proper cleaning and disinfection of vehicles moving between farms; and reports of rodents and small wild birds inside the poultry houses.

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