Montana wildlife officials have confirmed epizootic hemorrhagic disease and bluetongue in dead deer and pronghorn across south-central Montana, as the state's general deer and elk rifle season gets underway. Montana Fish, Wildlife and Parks said samples from several carcasses in its Region 5 tested positive for both viruses, with dead and dying animals found especially along rivers, according to the agency's Oct. 16 release published by Montana Outdoor.

Most cases are in Yellowstone and Big Horn counties, along the Yellowstone, Bighorn and Clarks Fork Yellowstone river corridors. White-tailed deer, mule deer and pronghorn have been affected. FWP has not released a count of dead animals.

For hunters, ranchers and landowners in the Billings area and beyond, the outbreak affects what they may find in the field this season. The general deer and elk season opened Oct. 24 and runs through Nov. 29, and FWP expects deaths to taper off as hard frosts arrive.

Midges, Water and a Warm September

Both diseases are caused by related viruses spread by tiny biting midges in the genus Culicoides. The insects breed in moist soil and mud along streams, ponds and stock tanks, which is why outbreaks often concentrate in river bottoms. Infected animals develop a high fever and severe dehydration, and many are found dead in or near water.

The outbreak follows a hot, dry stretch that kept midges active late into the season. Montana's September averaged 53.8 degrees Fahrenheit, 3.5 degrees above normal, and the state recorded its warmest 12-month period on record, according to NOAA data cited by Montana Free Press. Much of southeast Montana remains in extreme drought (D3), a category in which water sources shrink, and animals crowd the same muddy edges where midges breed.

State Climatologist Kelsey Jencso told Montana Free Press the drought ranks among the worst in a century, saying "Out of the last 100 years, only three or five years are worse." No formal study has linked this specific outbreak to climate change. The warm, dry conditions are consistent with what is known to favor midge activity and longer transmission seasons.

A Plains-Wide Outbreak, Milder in Montana

Montana is part of a much larger event — EHD has been unusually widespread this year across the northern Great Plains and upper Midwest. Wisconsin has reported at least 2,300 sick or dead deer, and South Dakota has reported 407 EHD deer deaths and is offering license refunds in 16 counties, Montana Free Press reported.

Montana's toll appears lighter than in some recent years. FWP Region 5 communications officer Chrissy Webb told Montana Free Press that recent outbreaks have produced high numbers of dead deer in river bottoms, but this year has not reached that extent. Game wardens have not conducted a detailed count. Across the region, Boston University's BEACON outbreak-monitoring project said the overall toll does not yet appear to rival the major EHD epizootics of 2007 and 2012.

Some widely shared reports of dead deer in northwest Montana describe a 2025 outbreak, not this year's. In 2026, FWP's confirmed cases are concentrated in the south-central part of the state, and Montana Free Press reported the Clark Fork River in western Montana was not currently affected.

Reporting Dead Deer and Handling Harvested Game

FWP says hunters and residents do not need to report additional suspected cases in Yellowstone and Big Horn counties, where the outbreak is already documented. Anyone who finds dead or sick deer or pronghorn in other south-central Montana counties should call the FWP Region 5 office in Billings at 406-247-2940. Reports from elsewhere in the state can go to the FWP Wildlife Health Lab at 406-577-7882.

Signs to watch for include animals that appear weak, disoriented, or unafraid of people, swelling of the head or neck, a bluish tongue, and carcasses clustered near water. Death can follow within days of the first symptoms, according to FWP's disease guidance.

The viruses do not infect people, and FWP says meat from animals that appear healthy at harvest is safe to eat when properly cooked. Hunters should not harvest or eat animals that look sick. FWP also advises against feeding meat from sick animals to dogs, since internal bleeding can make it unfit to eat.

Frost Ahead, Livestock to Watch

Relief usually comes with cold weather — a hard frost kills or suppresses midges, but symptoms can take up to 10 days to appear, so FWP warns that dead animals may still turn up for a couple of weeks after the first freeze.

Livestock owners should also pay attention. EHD rarely sickens cattle, goats or sheep, but bluetongue is a well-known disease of domestic sheep, goats and cattle, according to FWP. Producers in affected river valleys who notice lameness, fever, mouth sores or swelling in their animals should contact their veterinarian. No Montana Department of Livestock advisory on 2026 bluetongue in domestic animals had been issued as of Oct. 28.

Hunters planning trips to affected districts should expect some areas, especially river bottoms, to hold fewer white-tailed deer this year. Herds usually recover over several seasons, and FWP uses survey and harvest data to decide whether licenses or quotas need adjustment.

The bottom line: EHD and bluetongue are confirmed in south-central Montana deer and pronghorn after a hot, dry fall kept biting midges active. The viruses pose no risk to people, hunters outside Yellowstone and Big Horn counties should report sick or dead animals, and deaths are expected to fade with hard frosts in the coming weeks.

What Readers Want to Know

What is killing deer in Montana right now? FWP confirmed epizootic hemorrhagic disease and bluetongue in deer and pronghorn carcasses in south-central Montana, mainly Yellowstone and Big Horn counties.

Can people get EHD or bluetongue? No. The viruses do not infect humans.

Is deer meat safe to eat? FWP says meat from animals that appear healthy at harvest is safe when properly cooked. Do not harvest or eat animals that look sick.

Where should hunters report dead deer? In south-central counties other than Yellowstone and Big Horn, call FWP Region 5 at 406-247-2940. Elsewhere, call the Wildlife Health Lab at 406-577-7882.

Why are dead deer found near water? Infected animals run high fevers and become dehydrated, so they seek water. The midges that spread the viruses also breed in wet soil near water.

When will the outbreak end? Hard frosts usually stop transmission, though deaths can continue for about two weeks afterward. FWP expects deaths to subside in the coming weeks.