The U.S. Department of Agriculture released a recent report that the bird flu which devastated some Midwestern farms likely spread on machinery and workers, by rodents and possibly even on the wind.
Genetic properties of virus samples on more than 80 turkey and chicken farms were studied. The scientists determined that wild birds introduced the virus onto farm but bio security on farms and environmental factors likely contributed to the spread of the disease.
More than 49 million birds died or were etherized in 15 states as the virus spread from the Pacific Northwest into Midwest farms, making it the worst outbreak in the U.S. Hard hit were turkey farms in Minnesota, the nation's leading turkey grower, and chicken farms in Iowa, the leading egg producer.
The USDA says its staff found that infected and non-infected farms shared equipment, employees moved between then, and vehicles weren't disinfected when moving between farms. It also heard reports of rodents or small wild birds inside the poultry houses.
"USDA is collaborating with affected industries and states to implement more stringent bio security procedures while continuing to work on identifying and mitigating other possible disease pathways in poultry farms nationwide," the report said.
The scientists also found virus particles in the air samples collected outside of infected poultry houses, indicating the virus could be transmitted by air. Preliminary analysis of wind data "shows a relationship between sustained high winds and an increase in the number of infected farms approximately five days later," the report said.
The government is conducting additional analyses to better characterize environmental factors that may contribute to virus spread.