Newly released wastewater surveillance data suggests Michigan is a national hot spot for the highly pathogenic avian influenza virus that’s infecting poultry, dairy cows and other mammals across the US, and has also been identified in three farmworkers — two in Michigan.
Researchers told the Free Press they’re still trying to understand exactly why samples from all six of Michigan’s wastewater testing sites monitored by WastwaterSCAN show high levels of the H5 influenza A virus — the most detections of any of the 38 states with sampling sites — even in areas like Jackson and Warren, where there are no known H5N1 outbreaks among dairy cows, poultry or people this year.
“It’s clear that there’s something going on,” said Marisa Eisenberg, an associate professor in the departments of epidemiology, complex systems and mathematics at the University of Michigan. “We have had questions like: Are we having so much activity for H5N1 in general in Michigan because we’re looking for it or is it that we are really a hot spot? I think the wastewater is really telling us that we actually are seeing more activity for H5 than other places are.
Among the questions scientists are trying to answer:
WastewaterSCAN, which is based at Stanford University and monitors infectious diseases through wastewater systems, publicly posted the results of H5 influenza A virus testing of samples from 38 of the 50 states and the District of Columbia dating to May 21.
Only six states had detections of the virus in the wastewater — California, Idaho, Iowa, Minnesota, Michigan and Texas — as of Monday. Of them all, Michigan was the only state with high levels detected at each of its six testing sites: Ann Arbor, Jackson, Jenison, Mount Pleasant, Traverse City and Warren.
Even though Jackson County has yet to identify any infections among dairy cattle with the H5N1 influenza A virus, the highest number of positive wastewater samples, 10, were identified at the city of Jackson’s Wastewater Treatment Plant from May 21-June 9.
The city of Warren’s Wastewater Treatment Plant had the second highest number of H5 influenza detections in wastewater samples statewide with five identified from May 21-June 11, but Macomb County also has no known dairy cattle outbreaks.
The U.S. Centers for Disease Control and Prevention said Friday that blood sample tests suggest Americans have “extremely low to no population immunity” to the H5N1 virus strain circulating now. Seasonal flu vaccines don’t appear to have produced any antibodies to the virus.
That means “most of the population would be susceptible to infection from this virus if it were to start infecting people easily and spreading from person-to-person,” the CDC said.
Excrement doesn’t lie when it comes to infectious disease.
“Clearly, there’s a lot of virus in the wastewater,” said Richard Webby, director of the World Health Organization Collaborating Centre for Studies on the Ecology of Influenza in Animals and Birds and a member of the faculty at St. Jude Children’s Research Hospital.
Whether that virus is coming from waste runoff from cattle farms with infected cows or other animals, discharge of untreated milk into the wastewater system from production facilities, or someplace else, however, isn’t easy to untangle.
“The wastewater takes the genetic material from the virus and we know there’s a lot of genetic material from the virus in milk. Is it just milk being detected in the wastewater?” Webby hypothesized. “Somebody drinks milk, that goes through the digestive tract and is detected at the other end? Maybe.”
H5N1 viral particles have been identified in pasteurized milk in the commercial market, and though those particles are inactive and not capable of causing infection, it is possible they could be detected by testing samples of wastewater, said Alessandro Zulli, a postdoctoral scholar at Stanford University who works with WastewaterSCAN on research and wastewater sampling for viruses.
“There’s a good chance that the little sort of snippet that we measure, the amplicon, could still be present in wastewater,” Zulli said. “Now, that depends on a lot of factors. It depends on whether people are dumping a bunch of milk down the drain; it’s unlikely, I think, that it would pass through your entire digestive system without being further broken apart.”
Eisenberg agreed that Michigan’s high rate of H5 virus detections in wastewater isn’t likely driven by milk drinkers who’ve excreted viral particles into the wastewater system.
“Everyone is drinking milk” in every state nationally, she said. “So if it was just milk, regular milk that you’re buying at the store, I feel like we would be seeing much more widespread detections” across the US.
She is investigating whether milk production plants near Jackson and Warren discharge milk into the catchment areas where wastewater samples are drawn. Eisenberg said she is also curious about septage.
“Are there septic tank companies that … pull from septic tanks, but then it goes into the wastewater treatment plant?” she asked. “The wastewater treatment plants sometimes will accept septage from septic tank companies.
“We’re still at the hypothesis-generating stage. There’s some ponds and wetlands that go into the wastewater system. So could it be wild birds or is there some septage that’s coming from Jackson’s neighboring counties that have had cattle detections? Maybe it’s something like that?”
She wondered whether all the dairy farms in Jackson County have been tested for H5N1 infections, too.
“We’re still trying to get to the bottom of it,” Eisenberg said.
In Macomb County, Eisenberg said, some major dairy processing operations occur within the catchment area of the wastewater treatment plant in Warren, “which might explain the positives there.”
Webby said he doubts Michigan’s H5N1 outbreaks in poultry and cattle — or its high wastewater detections — are linked to migratory bird activity in the state. Michigan is part of the Mississippi Flyway.
“We can say with some certainty that it’s not because you’re a flyway,” Webby said. “This is based on looking at the sequences of the viruses that are available from this outbreak,” which suggest the virus is being spread from cow-to-cow and cow-to-person in the state, and not bird-to-cow or bird-to-person.
Zulli agreed that wild birds probably aren’t driving up H5 wastewater detections in Michigan.
“There is some speculation about how bird waste could get into the wastewater stream, but it’s unlikely,” he said. “In some of our previous retrospective studies, we haven’t been able to see it before from bird waste. I mean, of course, as it gets more widespread in birds, the chances of it actually ending up in the wastewater stream increase. But we currently don’t really think that it’s intrusion from bird wastewater so much as it is from either permitted discharges of dairy cattle farms or other runoff of that type.
“A lot more work is necessary before we can extrapolate and say where exactly it’s coming from or whether the contributions are from humans or animals.”
The wastewater data poses new questions as the H5N1 virus continues to spread nationally, infecting 92 dairy cattle herds in 12 states as of Friday and more than 96 million poultry in 48 states, according to the CDC.
In Michigan, H5N1 outbreaks have disrupted operations at 25 dairy cattle farms across 10 counties, cutting the animals’ milk production and eating into farmers’ already slim profit margins, according to the Michigan Department of Agriculture and Rural Development.
The state’s commercial egg and poultry farms also have felt the economic sting of the virus, as operations in 23 counties over the last two years have culled at least 6.8 million domestic birds infected with avian influenza.
So far, this strain of the avian influenza virus circulating in the U., identified as highly pathogenic avian influenza H5N1 clade 2.3.4.4b, has caused only mild illness in people who were infected after working closely with sick cows; all fully recovered. Two of the dairy farmworkers had eye infections, known as conjunctivitis or pink eye. A third reported upper respiratory tract symptoms. Federal and state health leaders say the risk among the general public is low.
The concern among many scientists, though, is how this virus is adapting and changing — and whether some of those changes might make it more infectious, allow for human-to-human transmission, reduce the effectiveness of current antiviral drugs or cause more severe illness or a higher mortality rate.
“Over the past 25 years of this virus, this is the most active form of virus we have ever had,” Webby said. “We’re seeing far more mammals infected with this virus in the past three years than we probably have over the whole 23 years before this. And now it has found its way into cows.
“Every corner we turn, this virus is teaching us something we didn’t know. This time, it’s that it can actually replicate in cows. … It was a surprise to most of us.
“Right now, it looks like it is still the virus that is in birds with maybe a few little changes. But we want to be able to know if this virus is changing, is it becoming more dangerous for humans? Is it becoming more dangerous for cows and other animals as well?”
The USDA published an epidemiological report Thursday based on Michigan’s dairy and poultry outbreak, and found that the virus likely is being spread by animal and human movement from farms with infected poultry and cows to those without.
The virus can hitch a ride from farm to farm on the soles of workers’ boots, on the wheels of cars, trucks and trailers as well as on farming equipment if they all are not cleaned and sanitized properly, the USDA found.
About 20% of the dairy farms the federal agency analyzed in Michigan shared workers with other farming operations and 13% had workers or family members who also worked on poultry farms. Many used veterinarians, nutritionists, feed consultants, milk haulers and other contractors who had direct contact with cattle on multiple dairy farms and shared vehicles across farms.
“Based on the epidemiological findings, the majority of links between affected dairy premises, and between dairy and poultry premises, are indirect from shared people, vehicles, and equipment,” the report said, recommending increased biosecurity practices and efforts to identify as many infected herds as possible.
But it’s not easy to get farm operators or farmworkers to agree to testing. And though Michigan has done more testing than many other states, that doesn’t fully explain why Michigan leads the nation in H5N1 infected dairy herds, people, and now, wastewater detections.
“I think there is a lot of surprise at the actual lack of testing that’s actually going on,” Webby said. “Other countries are in different positions where federal agencies can say, ‘I’m coming on your farm to test animals,’ which is not of course how it’s done here.”
Testing animals and people with symptoms is recommended, but not required in the US.
“From the perspective of an owner of a farm, I can understand to some extent some reluctance to test,” Webby said. “It is a disease that is not causing a lot of mortality on a farm. Any test right now can be associated, of course, with a quarantine period where cows can’t move and the substantial economic hit that comes with it, even though I think there are some funds coming available to help with that. So you can understand from an economic perspective, reluctance to test cows.
“With the humans, there’s probably some of that as well. … It’s a heavily sort of migrant population that works on the farms, perhaps with questionable documentation. The last thing that population wants to do is have anyone from any federal agency going out, and asking for any sort of name, phone numbers or addresses.”
But until there is more widespread testing of animals and people, Webby said, it’s difficult to answer a lot of the important questions that remain about this virus, such as: How is it moving around the farm? How long are cows infectious? What does it look like when cows get reinfected? Can they be reinfected?
“Without a lot more testing being done, we’re a bit hamstrung in understanding exactly what’s going on,” he said.
Michigan ranks in the top 10 nationally for dairy production. It is the biggest sector of the state’s agricultural economy, with $15.7 billion in annual economic activity, of which $2.7 billion comes from milk alone, according to MDARD.
“Fifteen percent of a dairy herd tends to test positive for this on an affected farm and there’s some corresponding drops in milk production,” said MDARD Director Tim Boring during testimony Wednesday before a joint meeting of the state House and Senate natural resources and agriculture committees. “Many cows never come back to full milk production. So we’re building out an understanding of what the economic impact for a lot of farms is.”
The USDA said 80% of farms with infected cattle reported abnormal lactation and less food intake; 90% of farms reported dairy cattle produced thickened or clotted milk.
State Rep. Jerry Neyer, R-Shepherd, whose family owns a dairy farm, said a decline of 15% of milk production in a herd could financially devastate farmers.
“For whatever reason, this virus seems to focus in on the mammary system in dairy,” he said. “That’s where it’s noticed, in production. It doesn’t seem to affect young livestock and non-milk production livestock cattle in the same way that affects the cow that’s producing.
“When you go off production even by just 10%, that’s your profit margin.”
And while there are losses in milk production to dairy farms, there also are increased costs for veterinary care for sick cows, for testing of animals and farmworkers, and costs to provide personal protective equipment to workers and test any who have symptoms. Some cows have lost pregnancies. Some have had to be put down.
Then there are the additional downstream effects.
“There’s a lot more time being spent tending to sick cows than doing things like planting corn or cutting silage or haylage in a timely fashion, and any number of additional aspects on farms that just aren’t getting done,” Boring said.
Farms with infected cattle also are required to take biosecurity measures to help ensure that when people enter or leave, they don’t bring the virus along with them on their clothing, vehicles or equipment. That means adding washing facilities. All of that costs money.
To soften the financial blow for affected Michigan dairy farms, Boring announced Wednesday that MDARD, in partnership with the USDA, will begin issuing $28,000 grants to 20 affected dairy cattle farms in the state.
“We know that the burden of working through questionnaires and having researchers on farms is significant,” Boring said. “So we’re looking to take some initial steps here and we’ll share details in the days to come … around what that looks like.”
Michigan’s commercial egg and poultry farms, an $8.5 billion industry in the state, haven’t escaped the avian influenza scourge, either.
Since the first Michigan flocks were infected in 2022, the virus has hit domestic poultry farms and backyard flocks in 23 counties. This year alone, there’ve been outbreaks in eight flocks across four counties — Newaygo, Gratiot, Ottawa and Ionia.
The virus behaves differently in birds, killing as many as 90% of domestic poultry that become infected.
“It is a fatal disease in birds and the simplest way to get rid of it, unfortunately, is just killing them or putting them down,” Neyer said. “In the long run, it is the kindest thing you can do. Until we have some type of vaccine for it, there isn’t much alternative to that.”
Farmers in Neyer’s 92nd state House District, which includes portions of Gratiot and Isabella counties, have been hit hard, by the virus, he said, with multiple outbreaks on both poultry and dairy farms.
Herbruck’s Poultry Ranch, the largest egg producer in Michigan and the 10th largest in the United States, temporarily laid off 400 of its workers in May after an avian influenza outbreak struck its flock, forcing it to kill hens and destroy eggs.
More:2nd Michigan farmworker has contracted avian influenza from cow, health officials say
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The good news, Boring said, is that the pace of new H5N1 outbreaks among commercial and backyard poultry flocks has slowed in Michigan. May 9 was the last time the virus was detected in a backyard flock in Ionia County. The last outbreak on a commercial poultry operation in Michigan was May 2 in Gratiot County, according to MDARD.
Because the virus has been infecting poultry for two years, the USDA has had time to stand up “really robust efforts in conjunction with state and industry partners … for animal disease preparedness and response,” Boring said. “There’s well-established procedures. There’s well-established capacity within the system to be responding in real time … based on response of the unique characteristics of how the disease manifests itself in poultry.”
There also are financial supports in place to help commercial poultry operations weather the economic hit they take when their entire flocks are culled as a result of infection.
“It’s going to be an evolving situation,” Boring said. “We’re going to be seeing concerns on this, I think, for a bit here, and we’re going to continue to really prioritize the work on the human health aspect for what those the potential (mutations) of the virus are. But I think that the piece to really focus on here is the fact that we’ve got effective food safety programs, human and animal safety programs. And the story here is the fact that the system is working as intended and protecting human and public health.”
Eisenberg said she and others at U-M are also working to create their own wastewater surveillance system of H5 viruses to help inform the state health department at sites in Jackson, Ann Arbor, Tecumseh and Flint.
“I’m expecting we’ll see positives for H5,” she said.
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