Update: Record EHD Death Toll Hits 1,600 Deer in 5 Wisconsin Counties

   The death toll from Wisconsin’s worst outbreak of epizootic hemorrhagic disease climbed past 1,600 the past three weeks, with the virus killing at least 500 more white-tailed deer while spreading into two more southeastern counties.

   As of Sept. 22, the Department of Natural Resources listed 1,100 EHD-killed whitetails in Washington County, up 57% from 700 on Sept. 4; 360 dead deer in Waukesha County, up 140% from 150; and 80 dead deer in Ozaukee County, up 166% from 30.

   The DNR also reported around 60 EHD deaths in Dodge County and around 10 EHD deaths in Milwaukee County. Neither county reported an EHD death in earlier reports.

   The outbreak is concentrated in northern Waukesha, and southern and central Washington counties; with other cases as far west as Juneau, as far north as Kewaskum and Belgium, and as far south as Genesee Depot and South Milwaukee.

   DNR disease specialists list only firsthand reports of dead deer in the agency’s totals. Erin Larson, the DNR’s deer-herd health specialist, said the agency reviews all dead-deer reports as they arrive to verify EHD was the likely cause. EHD-killed deer often die clustered near ponds, creeks or other waters, which they seek while suffering from high fevers and dehydration caused by the virus.

     Whitetails stricken with epizootic hemorrhagic disease often seek water to relieve severe dehydration and fatally high body temperatures.     — Snapshot Wisconsin photo

   Unlike chronic wasting disease, which reduces deer to skin and bones after about two years, EHD kills deer so quickly that they lose little weight before dying within a week. Therefore, the DNR dismisses EHD as the likely cause if a deer looks emaciated or has broken bones or injuries likely caused by collisions with vehicles. The agency also dismisses cases based merely on bad odors, second-hand reports, or duplicate reports in which two or more people find the same dead deer.

   Given the size of this outbreak, the DNR cannot verify dead-deer reports through onsite inspections. Larson said the DNR relies on citizens to accurately report unusual findings of dead deer to the agency’s wildlife switchboard through the Sick/Dead Wildlife Reporting Form, by emailing DNRWildlifeSwitchboard@wisconsin.gov, or by calling 608-267-0866.

   The EHD virus spreads through bites from small flies, a biting midge commonly called “no-see-ums.” Most EHD cases involve dead deer, but occasionally people report deer that appear dazed or lethargic, with their tongues hanging out, and foam or pink froth around the mouth.

   Most Wisconsin EHD cases occur in August and September, but this year’s outbreak started in late July, the earliest such deaths on record. EHD outbreaks usually wane in mid-September as temperatures drop, and end when early frosts kill biting insects. The state’s latest EHD case on file is Oct. 8.

   Though EHD can decimate whitetails on individual properties and parts of townships (36 square miles) deer herds typically rebound quickly, given the quality habitats generally found in southern Wisconsin. Since EHD first appeared in Wisconsin in 2002, it has never struck the same area two years in a row. Therefore, deer herds quickly replace EHD losses in subsequent breeding cycles.

   That disease pattern, however, also prevents Wisconsin deer from building the EHD antibodies that protect deer in Southern states, which suffer few losses during annual outbreaks. Therefore, when EHD occurs in Wisconsin — as well as Michigan, Minnesota, Illinois, Indiana, Ohio and Pennsylvania — the outbreaks can be far more deadly than those in Southern states, where most deer survive the virus.

   Larson said the DNR doesn’t plan to curtail bag limits or shorten deer seasons in response to the losses in southeastern counties. Hunters don’t have to shoot deer if they think EHD hit their area especially hard. But at the county level, deer numbers likely remain high. In Washington County, for example, where 43% of its 436 square miles is classified as deer range, hunters shot 2,943 deer in 2025. Further, the DNR estimated Washington County’s deer herd to number 16,200 this past winter, double its size from 2014.

   Likewise, in Waukesha County, where 42% of its 580 square miles is deer range, hunters killed 2,067 deer in 2025. The DNR estimated the county’s deer herd at 16,500 this past winter, double its size from 2017.

   Larson said EHD outbreaks remain impossible to predict, but drought and heat remain prerequisites for producing the midges that spread the virus. She said there’s no effective methods to prevent the disease, and to be wary of claims that commercial water treatments can block EHD by killing water-borne nutrients that feed the biting insects that spread the virus.

   In fact, Mark Ruder, director of the Southeastern Cooperative Wildlife Disease Study group at the University of Georgia, said scientists don’t know which wet habitats attract the various species of biting midges that spread EHD.

   “Just because a water body is there does not mean it’s a significant source for (those insects),” Ruder said in a note to the Wisconsin DNR. “Ponds are not always the sources people may think.”

   Ruder said his research in Kansas found that seeps and springs which create consistently muddy soil and small amounts of standing water produced the most biting midges. He didn’t think such sites could be effectively treated with chemicals.

   Larson said weather will dictate when the outbreak ends. Wisconsin’s EHD history is erratic. That first case in September 2002 involved 14 dead deer in a small area in Iowa County. Ten years passed before EHD struck again in Fall 2012, killing over 370 deer across 12 southcentral counties from late August to early October. Dane County reported 131 dead deer, followed by Columbia, 102; Waukesha, 49; Jefferson, 47; and Marquette, 12.

   Wisconsin’s next outbreak wasn’t until 2019, when the DNR recorded over 307 dead deer in seven counties, with the most in Crawford, 218; Vernon, 41; Grant, 20; and Sauk. 15.

   Subsequent outbreaks were smaller, with 77 dead deer in 2020 — 43 in Buffalo and 34 in Oconto counties; and less than 40 deaths in 2021, with less than 20 each in Juneau and La Crosse counties. Likewise, only four counties reported EHD-killed deer in 2024, with Jackson, Chippewa, Monroe and Waukesha counties ranging from three to 30 dead deer.