A second person in the U.S. has been infected with bird flu linked to dairy cows, the Michigan Department of Health and Human Services reported Wednesday.
The individual, a farmworker who had regular exposure to infected livestock, had mild symptoms and has recovered, the department said.
“The current health risk to the general public remains low,” Dr. Natasha Bagdasarian, Michigan’s chief medical executive, said in a press release. “We have not seen signs of sustained human-to-human transmission at this point. This is exactly how public health is meant to work, in early detection and monitoring of new and emerging illnesses.”
The individual was being monitored for symptoms following exposure to infected dairy cows, the Centers for Disease Control and Prevention said in a statement. The person developed conjunctivitis, or pink eye, and a sample taken from the eye tested positive for the virus.
This is the second instance of a person developing pink eye from a bird flu infection. That was also the only symptom seen in the Texas dairy worker who was diagnosed in March in the first documented case of the virus spreading from dairy cows to a human.
The CDC said that it’s sequencing samples taken from the Michigan worker to determine if the virus has mutated in ways that could allow it to spread more easily between people.
The Michigan Department of Agriculture and Rural Development confirmed additional cases in cows this week, bringing the total number of herds infected in the state to 19 as of Wednesday.
Nationally, at least 51 herds in nine states have been affected, according to the U.S. Department of Agriculture. In addition to herds in Michigan, dairy cattle in Colorado, Kansas, Idaho, New Mexico, North Carolina, Ohio, South Dakota and Texas have also tested positive for bird flu.
Federal health authorities are expected to hold a media briefing on the matter later Wednesday afternoon.
On Tuesday, the CDC’s principal deputy director, Dr. Nirav Shah, asked state and local health authorities in a call to continue monitoring for flu “at enhanced levels” throughout the summer, even though the typical flu season is over and testing for the virus falls to a minimum at this time of year.
The bird flu, also known as H5N1, is a type of influenza A virus.
Shah said that the CDC recommended that states “increase the number of positive influenza A virus samples submitted for subtyping to help detect even rare cases of human H5N1 virus infection in the community,” the agency said in a news release Tuesday.
Since the H5N1 virus was first identified in 1997, there have been just over 900 cases documented globally in humans. More than 50% of those patients died, according to the CDC. But that fatality rate may be an overestimate because cases may also be mild and possibly go undetected.
This is the third case of H5N1 overall in the United States. In 2022, an inmate in Colorado was diagnosed with the virus. The man was working on a commercial farm culling birds suspected to be infected. His only symptom was fatigue, and he recovered with a course of Tamiflu.
There is no evidence at this point that H5N1 is spreading from person to person. None of the people living with the Texas dairy worker became ill.
The CDC recommends that anyone in contact with dairy cattle wear protective equipment, including safety glasses, waterproof aprons and boots that can be sanitized.
