In African elephants, related forms of these viruses, which have been identified in wild populations, are generally benign, occasionally surfacing to cause small growths or lesions.

However, some types of EEHV can cause a highly fatal disease in Asian elephants, which kills up to 80% of severely affected individuals.

The first case of a fatal form of the disease was documented in 1990,[2] though tissue samples from as early as the 1980s have since tested positive for the virus, and localized skin lesions in wild African elephants were recorded in the 1970s.

The EEHVs are members of the Proboscivirus genus, a novel clade most closely related to the mammalian betaherpesviruses that have been responsible for as many as 70 deaths of both zoo and wild Asian elephants worldwide, especially in young calves.

[5][17] Studies have also detected both EEHV1A and EEHV1B as being shed in trunk wash secretions by healthy asymptomatic Asian zoo elephant herdmates of calves that previously had disease.

[4] An analysis of a number of North American cases, which ruled out the direct transmission of the virus between any of the affected facilities studied, strongly supported the idea of a significant Asian carrier population.

[8] In the former case, it produces small pinkish nodules on the head and trunk in juveniles, which appear for a few weeks and then regress, suggesting an intermittently reactivated localized infection that mostly remains dormant.

Symptoms include lethargy and an unwillingness to eat, a rapid heartbeat, and decreased blood-cell count, as well as cyanosis of the tongue, mouth ulcers, and oedema of the head and trunk.

[4][21] Prior to the development of the test, or in circumstances where it is not available, the disease may be misdiagnosed as any of a number of other conditions which have a quick onset leading to rapid death, including encephalomyocarditis and salmonellosis.

As a fraction of the overall population, it has been calculated that of the 78 Asian elephants born in captivity in North America between 1978 and 2007, 19 are known to have died of EEHV, and five more were successfully treated with antiviral medication.

In 2020, a 1-year-old Asian elephant named Ajay, from the Rosamond Gifford Zoo in Syracuse, New York, which was popular in the area, died from the virus.

[32] On 11th of December, the first test took place of a new vaccine developed by the University of Utrecht against the virus variant that only affects Asian elephants.