USDA Confident of Eradicating Virus, Although Bird Flu Count Keeps Climbing

Thirty people have contracted bird flu from exposure to infected animals this year, and more cases are expected, said the Centers for Disease Control on Thursday. At the same briefing, the USDA said it was confident of eradicating the viral disease in dairy herds despite the ever-rising number of outbreaks in California.

The No. 1 dairy state, California has accounted for 137 of the 339 infected herds nationwide, or 40%. In the past 30 days, it was home to 97 of the 101 outbreaks in 14 states nationwide. The other four were in Idaho. Some states have gone months without a new outbreak.

“We have seen effective elimination of the virus in herds,” said USDA bird flu adviser Eric Deeble. He declined to say the virus was under control in cattle, but said that “we think it’s unlikely” it will persist in the face of efforts to isolate infected herds to prevent the spread of the disease. Asked about his expression of confidence early this month about eliminating the virus in cattle, Deeble said, “Yes, I stand by that.”

California also leads the nation in human cases of bird flu, with 15, all of them workers on dairy farms. The U.S. total was 31, with 10 infections in Colorado, two in Washington, two in Michigan, one in Texas, and one in Missouri. The Missouri case was a puzzle because the patient had no known contact with animals. The CDC also said it was conducting confirmatory tests on suspected cases in five poultry workers in Washington.

Extensive serological tests of samples from health care workers involved in treating the Missouri patient found “no evidence of person-to-person” transmission of the avian flu virus, said Demetre Daskalakis, director of the CDC’s National Center for Immunization and Respiratory Diseases. A household contact became ill at the same time as the Missouri patient, suggesting a common exposure to the virus, he said. While the patient tested positive for bird flu, results were not definitive for the household contact. “This is sort of the end of what a lab can do,” Daskalakis said.

Serological tests look for antibodies that form in the blood following exposure to a virus. Public health officials say the risk of bird flu to the general population remains low. They are watching for changes in the makeup of the virus that would make it more infectious among humans, a potentially dangerous evolution.

Aside from the Missouri case, the human cases involved dairy and poultry workers employed on farms with infected herds and poultry flocks. All of the infected workers had mild symptoms, such as conjunctivitis, and none were hospitalized.

There have been reports of distressing death rates from bird flu among dairy cattle in California, several times higher than the 1 to 2% documented by the USDA earlier this year. “We have no specific evidence the H5N1 virus is acting differently,” said Deeble. A compounding factor in California might be the heat wave that has put additional stress on livestock, he said. At some farms in Tulare County, dead cattle are left along the roadside, said the Los Angeles Times earlier this week.

Two field trials for potential bird flu vaccines for dairy cattle are underway, said Deeble. More companies are expected to conduct similar research, he said.

Quest Diagnostics said it has been awarded CDC contracts that would allow it to offer consumer testing for the avian flu virus under a doctor’s prescription.

A CDC “spotlight” on the Missouri case is available here.

CDC guidance on how to reduce the risk of bird flu for people working with animals is available here.