The U.S. poultry industry may be facing the biggest outbreak of deadly bird flu in more than three decades, according to the World Organisation for Animal Health.
“They are dealing with a level of exposure that is probably unprecedented back to the outbreak in 1983 in Delaware and Pennsylvania,” said Brian Evans, a deputy director general at the Paris-based intergovernmental group known by its French acronym OIE.
New cases of the highly pathogenic avian influenza were reported Wednesday in Wisconsin, including 800,000 egg-laying hens, the second-biggest chicken flock detected during the outbreak. The number of U.S. commercial and backyard poultry flocks ravaged by the disease has climbed to more than 50.
An outbreak of another H5N2 virus in the Northeast in 1983 and 1984 resulted in the destruction of 17 million chickens, turkeys and guinea fowl to contain and eradicate the disease, according to the USDA. There’s no risk from cooked meat or eggs in the current outbreak, Evans said in a telephone interview.
The OIE has reported various strains of bird flu in 26 countries across the globe since Jan. 1, one of the most active years in terms of outbreaks since 2008, based on the group’s data. The U.S. and Canada have each reported three outbreaks.
The H5N2 strain has also been reported in Canada and parts of Asia, particularly Taiwan and China, Evans said. The genomic makeup “links it very closely” to a 2012 outbreak in Taiwan, he said.
“It’s a relatively stable strain that has been around for three, four years globally in both wild birds and other populations,” Evans said.
There have been no reported human cases related to the bird flu viruses circulating in North America, according to the World Health Organization. Human infections with avian influenza are “rare,” though they can’t be excluded, according to a WHO report on Tuesday.
The U.S. Centers for Disease Control and Prevention “considers that the risk to the general public from these outbreaks to be low at this time,” Alicia Fry of the CDC said Wednesday on a conference call alongside the USDA.
“That said, human infections with similar avian influenza viruses have occurred, and it is possible that we may see human infections with the viruses” after the U.S. outbreaks, said Fry, an epidemiology and prevention branch medical officer at the CDC’s National Center for Immunization and Respiratory Diseases in the influenza division.
Taiwan researchers found elevated antibodies against H5N2 in seven out of 141 people who had been in close contract with infected poultry in the 2012 outbreak, with two being the suspected result of subclinical infection.
Globally, “most human infections with avian influenza viruses have occurred in people with direct or close and prolonged contact with infected birds,” Fry of the CDC said.
The first cases in the U.S. and Canada were “no doubt” linked to migrating birds, probably waterfowl, passing a Mississippi River flyway, Evans of the OIE said. The subsequent increase probably involves both exposure to wild birds and sick poultry from neighboring farms, he said.
Measures to control the disease can include culling of infected birds and movement restrictions, or vaccination, and it’s up to countries to decide how to respond, Evans said.
Zoning and movement controls have proven effective in the past, while vaccinations have to be targeted to virus strains that are circulating, and don’t necessarily protect against other variants, he said.
“While we are cautiously optimistic that there will not be human cases, we must be prepared for that possibility, and we are taking routine preparedness steps including studying these viruses further and creating candidate vaccine viruses which could be used to make a vaccine for people if one were needed,” Fry of the CDC said. These measures are “routine,” she said.
A bird flu outbreak in the Netherlands that started in November and was contained by January through culls and transportation bans resulted in direct costs of 49 million to 56 million euros ($53 million to $60 million), according to agricultural researcher LEI Wageningen UR.
Controlling the disease will require “significant” cooperation between the U.S. poultry industry and the government, according to Evans, who said the OIE has “every confidence” the U.S. can contain the outbreak.
“Lessons are being re-learned,” Evans said. “There is a cost to biosecurity. If it’s in your backyard and you’re dealing with it, you pay a lot more attention.”
Sonstegard Foods Co. said on Monday that the flu affected many of its 3.8 million egg-laying chickens at the Sunrise Farms unit in Osceola County, Iowa.
Wisconsin also said Wednesday that flu was found in a flock of 87,000 turkeys in Jefferson County. Five cases have been reported in the state. On Monday, Governor Scott Walker authorized the National Guard to assist authorities in containing the outbreak.