A tiny biting fly nearly impossible to notice is contributing to a growing white-tailed deer die-off across Michigan this fall.
Epizootic hemorrhagic disease, better known as EHD, has now been confirmed in white-tailed deer in 12 Michigan counties during 2026, according to the Michigan Department of Natural Resources.
The disease is carried by tiny biting midges, sometimes called “no-see-ums,” that transmit the virus when they feed on deer.
What begins with the bite of an insect only a few millimeters long can end with sick deer developing high fevers, becoming severely dehydrated and dying near ponds, rivers and wetlands.
EHD Continues to Spread Across Michigan
Michigan confirmed its first EHD cases of the year in September, when infected deer were identified in Branch, Ingham, Jackson and Lenawee counties.
Since then, the list has grown considerably.
The Michigan DNR currently lists Allegan, Branch, Hillsdale, Ingham, Jackson, Lapeer, Lenawee, Montcalm, Oakland, Oceana, Saginaw and Washtenaw counties as having EHD-related deer mortality in 2026.
The disease can appear widespread on a county map, but its impact is often much more localized.
A heavily affected area may experience the deaths of numerous deer while another area just several miles away sees little or no mortality.
That unpredictability makes it difficult to know how severely a local deer population has been affected simply by looking at countywide numbers.
Dozens of Dead Deer Found Near Saginaw
One of the more dramatic reports this fall came from the Saginaw area, where dozens of deer were discovered dead along local waterways.
While fishing along the Cass River near the Shiawassee River State Game Area, Burton resident Ryan Mills encountered deer lying dead in the river and along its banks.
As he continued through the area, the number kept growing.
Mills estimated that he encountered at least 30 dead deer along the Cass and Saginaw rivers.
Some deer were already dead in the water while others reportedly appeared sick and disoriented.
Michigan DNR wildlife veterinarian Scott Larsen told Bridge Michigan that the deaths were strongly consistent with EHD.
At the time of the initial report, laboratory testing was still underway. Saginaw County has since been added to the Michigan DNR’s official list of counties with confirmed EHD mortality in 2026.
The DNR had received more than 1,200 reports of suspected EHD statewide by late September.
A Tiny Fly With a Deadly Bite
EHD does not spread directly from one deer to another.
Instead, the virus depends on a tiny insect known as a Culicoides biting midge.
The midges feed on blood. When one feeds on an infected animal and later bites another susceptible deer, it can transmit the virus.
These insects tend to reproduce around wet or muddy areas, creating ideal conditions for transmission during warm summer and early fall weather.
White-tailed deer are particularly susceptible to the disease.
Once infected, some deer may develop a high fever, weakness, swelling of the head or neck, excessive salivation, internal bleeding or sores inside the mouth.
Severely infected animals can deteriorate rapidly.
Why So Many Deer Are Found Near Water
One of the most recognizable signs of an EHD outbreak is the discovery of dead deer in or around water.
That can sometimes lead residents to wonder whether something in the water itself is killing the animals.
But the connection is usually much simpler.
EHD can cause an intense fever and dehydration. Sick deer often seek ponds, rivers, creeks and wetlands in an attempt to cool themselves or relieve their symptoms.
Some die shortly afterward.
That is why an EHD outbreak may leave several deer concentrated around the same water source even though the disease itself is being transmitted by biting midges rather than contaminated water.
Michigan’s DNR describes multiple deer dying in or around bodies of water as one of the characteristic patterns associated with the disease.
Michigan Has Faced EHD Before
EHD is not a new disease in Michigan.
The state first documented it in white-tailed deer in 1955.
After appearing only occasionally during the following decades, the disease returned in 2006 and has now been detected in Michigan during most years since then.
The state’s largest known outbreak occurred in 2012, when EHD-related mortality was documented in about 30 counties and an estimated 14,000 deer died.
Michigan confirmed EHD mortality in 15 counties in 2024 and 16 counties in 2025.
Twelve counties have been confirmed so far in 2026.
The final number could still change as additional sick and dead deer are reported and tested.
Cold Weather May Finally Stop the Spread
The biting midges responsible for transmitting EHD have one major weakness: freezing weather.
Michigan outbreaks usually develop during late summer and early fall, when warm conditions allow midge populations to remain active.
Once significant frost arrives, the insects begin dying off and transmission rapidly declines.
The DNR says EHD outbreaks generally end within about two weeks of the first killing frost.
Until then, additional deer may continue to become infected in affected areas.
What EHD Means for Michigan’s Deer Herd
Seeing dozens of dead deer in one location can make it appear that an entire regional deer population is collapsing.
Fortunately, EHD does not usually affect deer evenly across the landscape.
Some local herds can suffer significant mortality while populations nearby remain relatively untouched.
Michigan’s 2026 deer hunting preview warns that areas experiencing prolonged EHD activity can see substantial effects on local deer numbers, while locations only a short distance away may experience little impact.
For hunters and residents who regularly watch the same groups of deer year after year, however, a severe localized outbreak can be very noticeable.
A property that normally supports numerous deer may suddenly have significantly fewer animals after a particularly intense EHD season.
EHD Is Not Considered a Threat to People
Despite how severe EHD can be for white-tailed deer, the disease is not considered a human health threat.
The Michigan DNR says there is no evidence that people, household pets or other Michigan wildlife can contract EHD from infected deer.
Healthy deer harvested from areas where EHD has been documented are also considered safe to eat.
Wildlife officials still recommend that hunters never consume an animal that appears visibly sick.
EHD should also not be confused with chronic wasting disease, or CWD.
While both affect deer, they are completely different diseases with different causes and methods of transmission.
Residents Can Help Track the Outbreak
Michigan wildlife officials are asking residents to continue reporting sick or dead deer even in counties where EHD has already been confirmed.
Those reports help the DNR determine where outbreaks are occurring and how heavily individual areas may have been affected.
Reports can be submitted through the Michigan DNR’s Eyes in the Field diseased wildlife reporting system.
For wildlife officials, every report helps provide a clearer picture of an outbreak that can be difficult to measure from laboratory testing alone.
The insect responsible for the disease may be tiny, but the effect it can have on a local deer herd is anything but small.
For now, Michigan’s white-tailed deer remain vulnerable as the state waits for colder weather — and the hard frost that will finally bring another EHD season to an end.
Sources & Resources
Michigan Department of Natural Resources — Epizootic Hemorrhagic Disease in White-Tailed Deer
Current information on EHD, confirmed Michigan counties, transmission, historical outbreaks and reporting sick or dead deer.
Visit the Michigan DNR EHD page
Michigan Department of Natural Resources — DNR Confirms State’s First Cases of EHD for 2026
Michigan DNR announcement confirming the first 2026 cases and explaining how the disease spreads.
Read the Michigan DNR report
Bridge Michigan — Dozens of Deer Found Dead in Saginaw Area, Disease Suspected
Reporting on the discovery of at least 30 dead deer along the Cass and Saginaw rivers and the DNR’s investigation into EHD.
Read the Bridge Michigan report
Michigan Department of Natural Resources — 2026 Deer Hunting Preview
Information about how localized EHD outbreaks can affect Michigan deer populations and guidance for hunters.
Read the 2026 Deer Hunting Preview