Ten years after a deadly virus was first discovered in Australia, it has reared its ugly head once again. A horse near the Townsville area of Australia was diagnosed with Hendra virus, a deadly equine morbillivirus, on Dec. 14, 2004, and it was later euthanatized. A short time earlier, a veterinarian in the Cairns area was diagnosed with a mild case of the Hendra virus, but that individual later recovered.

Hendra virus, to this date, has only been found in Australia, and there have only been five reported outbreaks. The host of the virus appears to be fruit bats indigenous to Australia. According to Liz Smith, corporate communications director for Australia’s Department of Primary Industries and Fisheries, the outbreaks have coincided with fruit bat breeding season.

Smith says signs of Hendra virus infection, for the most part, are easily identified. “Signs to look out for in horses include respiratory distress, frothy nasal discharge, elevated heart rate, and increased body temperature,” says Smith. “Some neurological changes like head-pressing or twitching have occurred, and some cases have been initially thought to be colic.”

One factor that makes Hendra virus more potent is the fact it is a zoonotic disease, or a disease that is shared or transmitted between animals and humans. Christopher Olsen, DVM, PhD, associate professor of public health and an expert in veterinary virology at the University of Wisconsin, Madison, said, “There are still a lot of questions about the virus. It does affect both the respiratory tract and the central nervous system, so it’s likely that it can be aerosolized, but the exact routes of transmission have not been proven at this point. This is a very interesting virus in the sense that there have really only been a very small number of specific outbreaks and confirmed infections, so this is not a virus that is circulating widely within the horse population, even in Australia