CDC: Bird flu continues to spread, but risk low for humans

As bird flu continues to spread across commercial and backyard flocks, federal public health and agriculture officials stressed Wednesday that the food supply is safe and that the potential risk to humans is very low.

'However, human infections in similar strains have occurred and it is possible to see an outbreak when individuals have direct contact or close prolonged proximity with the birds,” said the Centers for Disease Control and Prevention's Dr. Alicia Fry, medical officer of the national center for immunization and respiratory diseases, influenza division, epidemiology and prevention.

More than 100 individuals are now being monitored, she said on a conference call with reporters on Wednesday morning.

Fry was joined by Dr. John Clifford, U.S. Department of Agriculture's chief veterinary officer, and Dr. David Swayne, USDA southeast poultry research lab director.

This strain of high pathogenic avian influenza H5N2 virus so far has spurred the euthanization of about 3.5 million turkeys and chickens in the Midwest. That figure does not include the 3.8 million egg laying hens that were be killed in northwest Iowa, which was reported Monday, Clifford said.

The birds are killed with foam or carbon dioxide, officials said.

In this most recent outbreak, H5N2 - typically spread by wild water fowl - began infecting birds in commercial flocks in the United States in mid-December 2014. Iowa recorded its first case of bird flu last week when the disease was found on a turkey farm in Buena Vista County, according to the USDA's website.

Monday marked the state's second confirmed incident and the largest single loss in the outbreak.

Meanwhile, some countries, including South Korean and China, have halted imports from the United States due to the outbreak, which Clifford said is the worst America has seen since the 1980s.

The Iowa Economic Development Authority explained that the confirmed cases of avian H5N2 means products produced in Iowa are not eligible to export.

Both the USDA and CDC are in early stages of vaccine development for birds and humans, officials said. The USDA has developed a 'seed strain,” which can be used as the foundation for a vaccine. The USDA's Swayne said this is a multi-step process, adding that the USDA is in the testing phase.

Because risk to humans is low, the CDC has identified candidate vaccine viruses that could be used if the virus were to spread to humans, Fry said. This is typical, she added, when new flu strains are identified.

'We are monitoring the situation closely as it's an evolving public health situation,” she said.

Officials believe the number of new cases will drop once 'warm temperatures are consistent” through the United States, noting that the virus cannot survive in heat. Sunny days also will help, as ultraviolet rays are able to kill the virus, they added.

The disease is carried by water fowl on their travels, which is why warmer weather is needed across the country.

It is possible for the virus to pick back up in the fall, officials said, but they were cautious to make any projections as to how it will affect flocks.

'We can't predict what will happen in the future,” Clifford said. 'But we are concerned.”