Second human case of bird flu linked to dairy cows found in Michigan

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 person, a farmworker who had regular exposure to infected livestock, had mild symptoms and has recovered, the health department said.

“The current health risk to the general public remains low," Dr. Natasha Bagdasarian, Michigan's chief medical executive, said in a news 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 person 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 pinkeye, and a sample taken from the eye tested positive for the virus. A sample taken from the person's nasal passages was negative.

At a news briefing Wednesday, Dr. Nirav Shah, the CDC’s principal deputy director, said the negative nasal sample is reassuring, in a sense.

"It reduces the likelihood — it does not eliminate, but it reduces the likelihood — of a respiratory route of transmission," Shah said.

It is the second instance of a person's developing pinkeye from a bird flu infection. That was also the only symptom 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.

More information about how the virus spread will be gleaned from its genetic sequence, including whether it has acquired any mutations that could allow it to spread between people more easily. The CDC is working to sequence samples of the virus taken from the Michigan worker and is expected carry out the genetic analysis later this week, Shah said.

"I don’t think this changes the risk picture in terms of the virus being transmitted to people and then transmitted among people," said infectious disease expert Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

Dawn O’Connell, the assistant secretary for preparedness and response at the Department of Health and Human Services, said at the news briefing that last week, the government had started the “fill and finish” process for about 4.8 million doses of a vaccine that is well-matched to the bird flu, the final step needed before vaccines are ready to distribute.