Michigan launches first effort of its kind to detect silent bird flu infections in farmworkers

Michigan has led the nation in making inroads with its farmers as it has worked to contain spread of H5N1 bird flu infections in dairy cows. Now the state’s health authorities are trying to do the same in looking for undetected infections among farmworkers.

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

Until recently, Michigan led the list of states with detected outbreaks in herds. But it hasn’t confirmed a new infected herd since June 7, and Idaho has since overtaken Michigan as the state with the most affected herds. Nationally there have been confirmed infections in 130 herds across 12 states since the outbreak in cows was first confirmed on March 25.

In that time, there have been two confirmed infections in farmworkers in Michigan, with a third in late March in Texas. But there have been anecdotal reports of additional farmworkers who have been sick with flu-like symptoms who have not been tested. The type of research that Michigan health officials have now undertaken, known as a seroprevalence or serology study, can start to define whether there have been undetected cases, and if there have, what activities may put workers at highest risk.

The study involves having workers complete a questionnaire that asks them about their activities at work and their contacts with cows and milk. Participating workers are also asked to give blood samples. Analysis of the blood samples will be conducted by laboratories at the Centers for Disease Control and Prevention, which is collaborating with Michigan on the study.

Natasha Bagdasarian, chief medical executive of Michigan’s Department of Health and Human Services, told STAT on Tuesday that the work — the first publicly disclosed such effort — should be considered a pilot or feasibility study. She declined to provide specifics about how many workers or how many farms have agreed to take part.

But whereas public health authorities have struggled to get permission to do this type of important work in many places, Bagdasarian said on some of the farms where her team is operating, people have come forward because they want to be tested.

“As we talk to farm owners and farmworkers, I’m actually getting questions like, ‘I have more people on my farm that would love to get tested’ and ‘Can we get additional people tested?’ People want this information,” said Bagdasarian, who is an infectious diseases specialist.

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

Bagdasarian, who spent part of Tuesday on a dairy farm, said the work is revealing that there is a lot of variation between the setups and procedures of different farms. Many do not have a lot of workers, she said, with those who are there taking part in feeding, milking, and administering medications to the animals.

“There are different types of equipment and different types of milking methods. And we have to try to understand those details in order to fully quantify what risk looks like 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.

“One really important piece of the work across the seroprevalence studies that we really want to do is that we have consistency in the testing and consistency in the survey,” he said during a press conference organized by the Department of Health and Human Services and the U.S. Department of Agriculture. “That collaboration with Michigan has been really important.”