Michigan launches first-of-its-kind initiative to detect silent bird flu infections among workers

MIchigan has made progress statewide in containing the spread of H5N1 avian influenza in dairy cows. Now state health officials are trying to do the same by looking for undetected infections among farmworkers.

The Michigan Department of Health is working with an undisclosed number of farms to assess the risk of workers becoming infected with the virus, which has spread to at least 25 farms in the state in the past three months.

Until recently, Michigan topped the list of states with confirmed outbreaks in herds. However, since June 7, no new infected herds have been confirmed there, and Idaho has now overtaken Michigan as the state with the most affected herds. Nationwide, infections have been confirmed in 130 herds in 12 states since the first outbreak in cows on March 25.

During that time, two cases of infection were confirmed among farmworkers in Michigan, and a third case in late March in Texas. But there are isolated reports of other farmworkers who became ill with flu-like symptoms and were not tested. The type of research that Michigan health officials have now conducted, known as a seroprevalence or serology study, can shed light on whether there are undetected cases and, if so, what jobs might put workers at highest risk.

As part of the study, workers must fill out a questionnaire about their work activities and their contact with cows and milk. Participating workers will also be asked to provide blood samples. Analysis of the blood samples will be performed by laboratories at the Centers for Disease Control and Prevention, which are collaborating with Michigan on the study.

Natasha Bagdasarian, chief medical officer for the Michigan Department of Health Services, told STAT on Tuesday that the work – the first publicly announced such effort – should be considered a pilot or feasibility study. She declined to provide details on how many workers or how many farms have agreed to participate.

But while health authorities in many places struggle to get approval for this important work, Bagdasarian says people are coming forward on some of the farms where her team works, wanting to be tested.

“When we talk to farm owners and farmworkers, I actually get questions like, ‘There are more people on my farm who would like to get tested,’ and ‘Can we get more people tested?’ People want that information,” says Bagdasarian, an infectious disease specialist.

“I talk to a lot of people who are really interested in understanding the transmission dynamics, who are really interested in having conversations and hearing what’s happening in other animal populations and in other states, and who are really interested in bringing together our collective knowledge to understand the transmission dynamics of disease,” she added.

Bagdasarian, who spent part of Tuesday at a dairy farm, said the work showed there were big differences between the facilities and procedures of different farms. Many don’t have many workers, she said, and those who do help feed, milk and administer medicine to the animals.

“There are different types of equipment and different milking methods. And we need to try to understand these details to fully quantify the risk to humans,” Bagdasarian said.

Demetre Daskalakis, director of the CDC’s National Center for Immunization and Respiratory Diseases, said the agency hopes other states will be able to conduct similarly structured studies.

“A really important part of the work in the seroprevalence studies that we really want to do is make sure we have consistency in the testing and the survey,” he said during a news conference organized by the Department of Health and Human Services and the U.S. Department of Agriculture. “This collaboration with Michigan has been really important.”