What's killing hundreds of deer? Here's what to know.

Show Caption More than 700 white-tailed deer have been reported dead in one Wisconsin county this summer, part of a growing outbreak that wildlife officials believe is being driven by a virus spread by tiny biting insects. The Wisconsin Department of Natural Resources (DNR) reports the outbreak, initially concentrated in Washington County, has now spread to Waukesha and Ozaukee counties. As of September 3, the DNR had received over 700 reports in Washington County, over 150 in Waukesha County, and just over 30 in Ozaukee County.

The disease is called epizootic hemorrhagic disease (EHD), affecting white-tailed deer and other hoofed animals through biting midges, often called "no-see-ums." In severe cases, EHD causes high fever, internal bleeding, and organ damage, leading to symptoms like weakness, heavy salivation, and foam around the nose. Infected deer often seek water. The DNR tested two deer from Washington County and confirmed both were positive for EHD.

The disease is less common in Wisconsin than in Southern and Western states, and Wisconsin deer have historically been less exposed to it. Death rates can be higher in areas where EHD is rare, and high deer population densities also increase mortality. Wisconsin first confirmed EHD in 2002, with sporadic outbreaks since then.

The disease usually fades after the first hard frost, killing the transmitting midges. Survivors may develop antibodies to withstand future outbreaks. EHD is not the same as chronic wasting disease (CWD), which is caused by prions and spreads through infected animals and environments.

CWD progresses slowly and is fatal, while EHD causes rapid illness and death. The virus does not infect humans, posing no risk from handling infected deer or eating venison. The DNR encourages residents to report unusual numbers of sick or dead deer to aid monitoring.

Contributing reporters include Paul A. Smith and Anthony Thompson.

Source: USA Today