Michigan dairy worker infected with bird flu in third human case associated with outbreak among cows

Another Michigan dairy worker has been infected with a highly virulent bird flu, marking the third human case since the disease was detected in dairy cattle this spring but the first to report symptoms of respiratory illness.

The worker reported having a cough and eye discomfort with watery discharge, and received an antiviral treatment, the Centers for Disease Control and Prevention said Thursday. The person is isolating at home and symptoms are resolving, the agency said. Those living in the worker’s home have not developed symptoms; no other workers at the farm have reported symptoms, and staff are being monitored.

Nirav Shah, the CDC’s principal deputy director, said the emergence of respiratory symptoms “is not atypical” of novel influenza viruses.

“What the presence of respiratory symptoms tells us is that the exposure risk is higher,” he said. “Simply put, someone who’s coughing may be more likely to transmit the virus than someone who has an eye infection.”

Dairy workers infected in the previous cases — in Texas in April and in Michigan last week — reported eye inflammation. Federal health officials say the development underscores the need for workers to take precautions — such as wearing personal protective equipment — when working with cattle.

The two workers infected with the virus in Michigan were not wearing full protective equipment, state officials said. In the previous case, infected milk splashed directly into the worker’s eye, resulting in inflammation. The latest worker to be infected, who is employed on a different farm, also had direct exposure to an infected cow but no further details were released.

Additional cases are expected, federal officials said, since public health surveillance kicked into gear in April. But the new case underscores the elevated risk for farm and dairy workers. The CDC reiterated that it believes the risk to the general public is low, and there is no indication of person-to-person spread.

Testing cows is key to controlling the outbreak, public health officials have said, amid frustration that more livestock herds aren’t being tested. The USDA had previously announced financial incentives to prod farm owners to test cows more broadly, even if infections have not been reported.

The USDA on Thursday announced a voluntary pilot program beginning next week to expand testing of herds not known to be infected with the H5N1 virus. Dairy producers enrolled in the program will be granted greater flexibility to transport lactating cows across state lines if tests of their bulk milk tanks are negative for the virus three weeks in a row and continue to remain negative in weekly tests.

“This program is not loosening restrictions, but rather gives producers greater certainty and USDA better visibility onto the status of herds and the virus by providing this ongoing testing,” said Eric Deeble, USDA’s acting senior adviser for highly pathogenic avian influenza.

The USDA also unveiled $824 million in funding aimed at protecting livestock health, such as surveillance and the department’s effort to develop vaccines for animals for the highly pathogenic avian influenza.

The bird flu was detected in U.S. dairy cattle for the first time in late March, though researchers say the virus had probably been circulating on a limited basis for about four months before federal officials confirmed the disease. The H5N1 virus has now been detected in herds in nine states.

In the latest human case, specimens collected from the patient tested positive for avian flu at the state department’s laboratory. The specimen was then sent to the CDC, which confirmed the infection Wednesday night.

The development marks only the fourth case of the bird flu virus in the United States. In 2022, a poultry worker in Colorado tested positive for the same strain of avian influenza. Across the world, cases of human illness have ranged from mild infections to more severe illness, like pneumonia.