A worker on a Michigan dairy farm contracted a mild case of H5 bird flu from infected cattle — the second cow-to-human infection since bird flu was first identified in dairy cattle in late March — said the Centers for Disease Control on Wednesday. The risk to the public remains low, said Nirav Shah, the CDC’s principal deputy director.
Also on Wednesday, the USDA broadened its efforts to quell the spread of the virus by extending its offer of financial assistance to dairy farmers to include uninfected herds. To date, the H5N1 bird flu virus has been confirmed in 52 herds in eight states. Michigan has the most, 15, followed by 14 in Texas, where scientists say the highly pathogenic avian influenza virus jumped from birds to cattle in late 2023 or early this year.
“This [second] case was not unexpected,” said Shah during a teleconference. “It does not change our assessment of the risk overall” and “does not suggest we are any steps closer to anything larger.” Cow-to-human transmission is rare, there has been no human-to-human infection, and the volume of flu-like illnesses being detected is unchanged, he said, when asked if there was a risk of widespread illness.
While the risk to the general public is low, the risk is higher for farm and slaughterhouse workers and for people with close, prolonged, and unprotected exposure to infected birds and other animals. Dawn O’Connell, assistant secretary of the Department of Health and Human Services, said that a couple of weeks ago, as a precaution, the federal disease stockpile ordered 4.8 million doses of vaccine against bird flu. There are no immediate plans to use the vaccine, said O’Connell and Shah. The CDC recommends livestock workers wear personal protective equipment, such as gloves and face shields.
Dairy workers were infected in both cases of cow-to-human transmission, and the Michigan worker, like the first infected worker, in Texas, reported conjunctivitis — redness of the eye. “They are doing well,” said Shah, referring to the unnamed Michigan worker. A nasal swab from the worker tested negative while an eye swab tested positive for the H5 virus.
“It reduces the likelihood of a respiratory route of transmission,” said Shah.
The Texas farmworker infection, reported on April 1, was the first known cow-to-human H5N1 bird flu transmission in the world. In 2022, there was a U.S. case of poultry-to-human transmission of bird flu.
The Michigan worker was enrolled in a so-called active monitoring program that included daily contact via text message. The worker reported eye redness. Forty people have been tested for the bird flu virus since late March, said Shah.
USDA official Eric Deeble said dairy farmers with uninfected herds would be eligible for up to $1,500 per farm to develop and implement a biosecurity plan for their herds; up to $2,000 per farm to cover the veterinary costs of collecting samples for H5N1 virus tests; up to $100 per month for the cost of shipping the samples to approved laboratories; and $100 for an in-line milk sampler. On May 10, the USDA announced up to $28,000 over three months would be available to help dairy farmers cope with infected herds. The USDA has mandated the testing of lactating cows for the H5N1 virus before they are shipped across state lines.
A Michigan dairy farmer with a 500-cow herd estimated costs of $30,000 to $40,000 in two weeks of combating the virus on his farm. “There has been the loss of milk, loss of quality premium, increased labor, and loss of a few pregnancies resulting in culling animals,” reported Michigan State University Extension. “Based on the number of cows with elevated temperatures and subtracting out the normal rate, they believe 40 percent of the lactating herd was infected.”
MSU Extension quoted the farmer as saying, “It has been a lot of work, stressful on the cows and frankly overwhelming.”
Dairy cows with bird flu often develop a fever, lose their appetite, and produce markedly less milk. Officials have said that cows recover after a couple of weeks. MSU Extension cited a report of symptoms persisting for four to six weeks.