Bird flu found in Michigan dairy worker, second U.S. case in 2 months

A Michigan dairy worker has been infected with a highly virulent bird flu, the second human case in less than two months of the H5N1 virus circulating among dairy cows.

Federal officials said Wednesday that the case does not change their assessment that the risk to the general public remains low. But in a sign of increased urgency, they announced additional financial incentives for dairy producers to expand testing of cattle and accelerated the timetable to ready nearly 5 million doses of vaccine in case the virus becomes more widespread among people.

The second case did not come as a surprise, officials said, because public health surveillance has been monitoring for additional cases since April, when federal officials announced a dairy worker in Texas was being treated for bird flu shortly after the highly pathogenic avian influenza had been identified in U.S. dairy cattle for the first time.

“We found this case because we were looking for it. We found it because we were prepared,” Nirav Shah, principal deputy director at the Centers for Disease Control and Prevention, said during a news briefing Wednesday.

Shah recognized Michigan officials for their actions. The state has enrolled 170 farmworkers into its active monitoring program, where individuals receive a daily text from the health department asking if they are having symptoms, Shah said. When this worker indicated they were having symptoms, Michigan health officials responded quickly, including with testing, he said.

The Michigan worker, like the one in Texas, experienced mild eye symptoms and has since recovered, according to state officials. A nasal swab of the worker had tested negative for influenza in Michigan, but an eye swab was shipped to the CDC in Atlanta, where it tested positive for avian flu, indicating an eye infection, according to the agency.

Federal health officials said they do not know how the worker became infected or if the individual was wearing protective eye equipment. In dairy farm parlors, workers typically express milk by hand from cow teats before attaching milking equipment. A splash of contaminated milk could get into the eye directly, or by touching the eye with a hand contaminated with virus. Eye infections have been associated with previous human infections of bird flu. Michigan’s health department declined to provide details, citing the need to protect the worker’s privacy.

The Michigan worker’s case - with virus found in the eye swab but none in the nose - is reassuring in one sense, Shah said, because it reduces the likelihood of a respiratory route of transmission. Respiratory spread would make the virus more contagious.

CDC officials said the case underscores the importance of personal protective equipment being used by workers at dairy farms and slaughter facilities. Federal and state officials have made supplies available to dairy farms but have not required their use.

Researchers say the virus had probably been circulating in dairy cattle on a limited basis for about four months before federal officials confirmed the disease in cows in March. The virus has been confirmed in 51 dairy herds in nine states, according to the Agriculture Department. Eighteen of the herds were in Michigan.

The Michigan case marks only the third human case of the H5N1 virus in the United States. In 2022, a poultry worker in Colorado tested positive for the same strain of avian flu. Cases of human illness from H5N1 bird flu have ranged from mild infections - such as eye infections - to more severe illness, such as pneumonia, which has resulted in death in other countries.

Some government officials and public health experts have been frustrated that more livestock herds aren’t being tested and that results of tests that are conducted are not being shared quickly enough. In response, the federal government in May unveiled $98 million in financial incentives aimed at encouraging more testing of cattle and beefing up biosecurity protocols on farms to control the growing outbreak.

On Wednesday, the Agriculture Department announced several incentives for farms without infected dairy cows, including up to $1,500 per farm to implement biosecurity plans and up to $2,000 per farm for veterinarians to collect samples for H5N1 testing. Additionally, all farms will be eligible for a new program to compensate for the milk that their cows don’t produce because of illness.

The federal government is not planning to vaccinate workers and others who come into close contact with dairy cattle, officials said. But Dawn O’Connell, head of the Administration for Strategic Preparedness and Response, said the agency has found a manufacturer to prepare 4.8 million doses of bird flu vaccine, a process that would take “a couple of months.”

Factors that could prompt a vaccination campaign include increased transmission from animal to human, evidence of human-to-human transmission or a human case of H5N1 without any link to a dairy farm, Shah said.

The CDC and public health officials plan to continue enhanced flu monitoring through the summer to detect rare cases of human H5N1 infection.