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Research Snapshot: Confirming airborne transmission of influenza A virus in swine

It’s long been believed that, as in people, airborne transmission can be responsible for outbreaks of the flu virus in swine. Now, University of Minnesota researchers have helped shift such belief to scientifically-proven fact.

In a new study published today in the open-access online publication PLoS ONE, researchers from the University of Minnesota’s College of Veterinary Medicine (CVM) document the detection and isolation of airborne flu virus at four acutely infected pig farms. Furthermore, they demonstrate the airborne nature of the virus by confirming the presence of virus in air samples from inside swine barns, at the barn’s external exhaust fans and downwind from the farms at distances up to 1.3 miles away.

The research should help improve the design of flu control strategies (such as biosecurity containment systems) and strengthen research into the prevention of zoonotic infections.

“There are a number of implications of this study, the first being that we’ve confirmed airborne transmission as an important route of transmission of influenza in pigs,” said Montserrat Torremorell, D.V.M., Ph.D., the CVM’s Allen D. Leman Chair in Swine Health and Productivity. “We’ve also identified a potential exposure source to people and have highlighted the role of pigs in the overall transmission of influenza.”

The virus, which in many ways resembles the flu we humans strive to combat, is characterized by fever, sneezing, coughing and a runny nose. Infected swine are also often lethargic and won’t eat at a level that can support weight gain. As a result, many pigs have variations in their weight which can have profound repercussions for pig farmers.

According to the study’s authors, their work is the first to report that pigs battling influenza will release viral particles into the air that can leave their barns through exhaust systems and travel downwind. It’s not hard to extrapolate the impact of a virus traveling in such a way.

Prior research has shown swine farm density contributes to the spread of flu, and in areas where many farms are located in close proximity, the ability of flu virus to travel more than a mile could generate serious issues for nearby hog farms.

The authors note that “how the levels of viral genetic material relate to risk of transmission to other pigs or other species including humans needs further research and is beyond the scope of [the current] study.”

The following CVM researchers and former U of M faculty contributed to this study:

  • Cesar A. Corzo, D.V.M., Ph.D. candidate
  • Marie Culhane, D.V.M., Ph.D., associate clinical professor of veterinary population medicine
  • Scott Dee, D.V.M., Ph.D.
  • Robert B. Morrison, Ph.D., professor of veterinary population medicine
  • Montserrat Torremorell, D.V.M., Ph.D., associate professor of veterinary population medicine

Funding for this research was provided by the Rapid Agricultural Response Fund – Minnesota Agricultural Experiment Station and the University of Minnesota Swine Disease Eradication Center.

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