 Outbreaks in Indiana of the disease can be characterized by both significant outbreaks that occur on a 5-10 year cycle that affect the entire state and smaller outbreaks that may only involve a few counties.Transmission of EHD occurs by a host being bitten by a virus-carrying fly or midge.There are many different species of culicoides that can carry this virus, however, the most common carrier is thought to be culicoides variipennis.