Although California reported outbreaks of bird flu in 12 dairy herds last week, most states have gone weeks without new cases being discovered, including those with high levels of scrutiny, according to USDA data. Agriculture deputy undersecretary Eric Deeble cited Colorado and Michigan as examples of the tailing off of infections and said during a multi-agency teleconference that “this decrease gives us confidence” of eliminating the virus in dairy cattle by isolating herds.
Colorado leads with nation with 64 infected herds but has not reported an outbreak since Aug. 13, said a USDA database. The most recent outbreak in Michigan, which is third in the nation with 29 cases, was Sept. 9. California is second in the nation for outbreaks and accounts for one-fifth of the 256 herds in 14 states.
The Centers for Disease Control said on Friday that two dairy farmworkers in California were infected by the avian flu virus. The outbreaks were “not unexpected” given that there were 56 infected herds in the state, said Nirav Shah, the CDC’s principal deputy director, during the teleconference. “Both workers are dairy workers at different dairy farms. Both individuals experienced mild symptoms.” Shah said the workers had conjunctivitis — pink eye — and were given antiviral medications and were recovering.
Sixteen human cases of bird flu have been reported nationally this year, all but one of them, in Missouri, in dairy and poultry workers. The Missouri infection involved a patient with no known contact with animals. The CDC said results were expected in mid to late October from blood tests of healthcare workers who developed symptoms after being involved with treating the patient.
Scientists identified the H5N1 avian flu virus in late March as a mysterious disease circulating among dairy herds in Texas. The jump to cattle from birds increased the opportunity for the virus to become more communicable to humans. The Missouri case raised the question of person-to-person spread. The CDC underlined that only one case of bird flu has been confirmed in Missouri at a time of the year when respiratory infections are common.
As a step to combat bird flu in dairy cattle, Colorado has required weekly tests of samples of milk taken from bulk storage tanks on dairy farms since late July. California has ordered bulk tank tests at dairy farms that are within six miles of an infected herd. Michigan gave farmers the option of bulk tank tests or testing of cows individually if they wanted to exhibit dairy cattle at a fair.
Deeble said bulk tank tests typically bring an initial surge of detections followed by a rapid drop-off. The USDA strategy against bird flu in cattle is to use stepped-up biosecurity measures to prevent infection of herds, and if an outbreak occurs, to isolate on the infected farm until the infection dies out.
In California, between 10 and 15 percent of infected dairy cows are dying of bird flu, far more than the 1 or 2 percent mortality that has been reported elsewhere, and a larger portion of herds, as high as 50 or 60 percent, were becoming ill, said the Los Angeles Times, based on information from veterinarians and dairy industry observers.
“It’s spreading very efficiently now among mammals, and it’s mutating and adapting to mammals as it does,” said virologist Rick Bright, former head of the U.S. Biomedical Advanced Research and Development Authority. “This virus is out of control … The concept of letting it burn out through food animals, with unmonitored voluntary testing, has failed. There are pandemic playbooks that we need to dust off and begin to implement.”
Also during the teleconference, the Department of Health and Human Services said it awarded $72 million to three vaccine companies to double the U.S. stockpile of H5N1 vaccines to 10 million doses by spring 2025. The HHS also announced a research agenda in partnership with the USDA to study how the bird flu virus spreads and prevent transmission of the virus among people and animals.