Epizootic hemorrhagic disease virus, often abbreviated to EHDV, is a species of the genus Orbivirus, a member of the family Reoviridae.

[1] It is often mistakenly referred to as “bluetongue virus” (BTV), another Orbivirus that like EHDV causes the host to develop a characteristic blue tongue due to systemic hemorrhaging and lack of oxygen in the blood.

[3] Historically, only serotypes EHDV-1 and EHDV-2 have been found in North America, but recent research has discovered at least one more in the Midwest and Southern United States.

The first identified outbreak of EHDV in the United States in 1955 caused several hundred white-tailed deer to die in New Jersey and Michigan.

Epizootic hemorrhagic disease virus belongs to the family Reoviridae, a family of double-stranded RNA viruses that includes familiar genera Rotavirus (the most common cause of viral gastroenteritis in children), Coltivirus (causative agent of Colorado tick fever), and Orbivirus.

[8] The virion outer layer is composed primarily of VP2 and VP5 trimers that are also involved in the virus's ability to attach to and penetrate a host cell.

EHDV-6 is thought to be a hybrid form where each of the collected type-6 viruses were all reassortants containing VP2 and VP5 derived from an exotic EHDV-6, while the remaining structural and nonstructural proteins were obtained from the indigenous EHDV-2.

These symptoms develop about 7 days after the animal was exposed to the virus and 8–36 hours after the onset of initial observable signs; deer progress into a shock-like state, collapse and die.

Increased pericardial fluid and generalized edema consistently found in all cases of EHDV strongly suggest its interference with the normal circulation of blood.

Virus samples can be isolated from many kinds of tissues from infected animals, including blood, liver, spleen, kidney, lung, heart, and other muscles.

[12] VP5 often catalyzes cell fusion, which facilitates the penetration of the endosomal membrane and consequently the release of outer capsid components.

[16] In order to bypass these host defenses, double-stranded RNA viruses such as EHDV “hide” their genome and other translation machinery within closed protein capsids.

The release of EHDV occurs through two main mechanisms: the common viral pathway of budding and by direct cell membrane penetration.