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Illinois Department of Natural Resources
August 2020
August 3, 2020

EHD in Illinois – Summer 2020

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By Doug Dufford

Each year between August and October, especially during hot and dry summers, landowners, deer hunters and wildlife enthusiasts are keeping an eye open for signs of an outbreak of Epizootic Hemorrhagic Disease (EHD) in the local white-tailed deer herd.

A table indicating suspected Epizootic Hemorrhagic Disease cases in Illinois between 2005 to 2019.

The Illinois Department of Natural Resources (IDNR) continually monitors the status of this disease with the assistance of the many individuals who report dead deer observed in the field. In 2018, EHD activity was relatively low, with a limited number of reports coming from west central and southern Illinois; the three highest EHD infection years came in 2012, 2007 and 2013 (see table).

EHD is an acute, infectious and often fatal viral disease of some wild ruminants, including white-tailed deer. Characterized by extensive hemorrhages, this disease has been responsible for significant outbreaks in deer in the northern United States and southern Canada. Affected animals develop a fever, and typically many are found in, or adjacent to, water where they try to reduce their body temperature. Death can come quickly, from 8 to 36 hours after the onset of observable signs, to some infected deer. Other deer may die days or weeks later, and some will completely recover.

EHD is observed somewhere in Illinois every year, typically where receding water levels provide the muddy shoreline breeding habitat necessary for the EHD vector, a Culicoides biting gnat. EHD is transmitted when a gnat carrying the virus bites a deer. Outbreaks tend to be localized because environmental and habitat conditions play an important role in producing the right mix of virus, high gnat populations and susceptible deer. An insect-killing frost typically ends an EHD outbreak.

A map of Illinois counties colored in yellow or orange to indicate which counties have reports of Epizootic Hemorrhagic Disease in deer.

Signs of EHD appear about seven days after the deer has been bitten and include sluggishness, difficulty breathing, loss of appetite, salivation and swelling of the head, neck, tongue or eyelids.

EHD cannot be transmitted directly from deer to deer and is not considered to be hazardous to humans or pets.

The patchy annual distribution of EHD means that Illinois residents are key to tracking annual outbreaks. Illinois residents and hunters serve as IDNR’s eyes and ears in monitoring the annual distribution of this disease, as well as the health of the local deer herd.

To learn more about EHD, or report incidences of sick and dead deer, access the online Report Sick or Dead Deer reporting form at White-tailed Deer Illinois. You will be asked to report facts including the county, number, age, and sex of dead deer and specific location of the deer.


Doug Dufford retired from the Illinois Department of Natural Resources’ Division of Wildlife Resources, having serve as the Wildlife Disease and Invasive Species Program Manager. He continues to provide technical support on contract.

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