New Study Says Bird Flu Spread by Wind, Humans, Fowl

Jun 16, 2015

Agriculture officials don’t know just how the massive outbreak of avian flu in the Midwest was spread, but they believe the culprits include humans breaking biosecurity measures and the virus going airborne.

Up to this point, officials had blamed the introduction and spread of the virulent highly pathogenic H5N2 virus on migratory birds. A preliminary study released Monday said researchers had found no “specific pathway” that lead to the largest outbreak of avian influenza in the U.S.

Most interesting was a finding “supporting the idea that the virus can be transmitted through air.” Researchers found that the virus was spread up to a half-mile (700 to 1,000 meters) during two windy days that “appeared to be related to clusters of outbreaks five to seven days later."

Scientists knew from past cases that the bird flu virus could be carried in the wind, on dust or feathers, for just a few hundred feet, said T.J. Myers, associate deputy administrator of veterinary services for the USDA’s Animal and Plant Health Inspection Service.

“If we are seeing spread from farm-to-farm that’s further apart than that, this would be something that we haven’t seen before, at least over those distances,” Myers said in a phone interview.

An airborne virus means companies would have to change some procedures in their large barns that can house tens of thousands of birds. For instance, the companies might need to change their ventilation systems, Myers said, placing filters or blocks on the large vents and fans on the poultry barns.

The largest outbreak of bird flu in the U.S. has ravaged the egg and turkey industries in the upper Midwest, resulting in the killing of nearly 47 million birds. The virus has not spread to humans and scientists say that risk is very low. (Click here for the USDA’s fact sheet on avian influenza.)

Although Ag Secretary Tom Vilsack had speculated earlier that the virus might have been spread by humans, USDA veterinarians hadn’t yet pointed to possible spreading by, for instance, workers on the farms or those driving trucks between infected areas.  The study confirmed that biosecurity measures were broken.

“APHIS has observed sharing of equipment between an infected and non-infected farm, employees moving between infected and non-infected farms, lack of cleaning and disinfection of vehicles moving between farms, and reports of rodents or small wild birds inside poultry houses."

The current outbreak and rapid spread by “environmental factors" has changed the mantra of biosecurity, Myers said. Instead of trying to prevent the disease from coming on a property, now producers must be concerned about the pathogen moving from barn to barn on each farm.

“What that means is producers have to think a little bit differently about biosecurity in this case,” he said. “It’s not at the farm gate where you need to be concerned. It’s at the barn door.”