Hendra Virus Disease — Rare Diseases Spotlight #1
In September 1994, down in the suburbs of Brisbane, Australia, a curious case emerged. Thirteen horses and a trainer were killed by an illness unseen before in the history of mankind. The trainer, whose name was Victory Robert Rail, was theorized to have been exposed to the index case, which was a mare. He was urged by his wife to seek medical treatment when he started to develop the symptoms presented by the horses. Unfortunately, within a week of the first horse’s death, Rail passed away from complications caused by the disease. Samples were retrieved and studied extensively. The mysterious virus would later bear the name “Hendra virus." This would spark a wave of fear over the Australians, which even led to the coinage of “Hendra Season,” a term that referred to the increase of Hendra virus cases from the months of May to October. How could a virus shroud an entire country in panic and distress? Keep reading to learn more.
Hendra Virus Disease (HeV) is a zoonotic disease that is known to affect the respiratory system and the nervous system. Its natural reservoir is the fruit bats of the Pteporus genus, or, informally, flying foxes. The disease is generally lethal in horses and humans, with a mortality rate of 75% (although the mortality rate in horses is not highly precise due to the immediate euthanasia of infected horses) and 57%, respectively. When a person comes into contact with an infected horse, the disease may be transmitted through the various bodily fluids of the horse, some of which include saliva, urine, mucus, etc. Once a human has contracted the disease, HeV will have an incubation period of 9–16 days before symptoms arise. It will first manifest as a mild flu-like illness, which will frequently worsen and cause respiratory distress. The disease, as seen in numerous cases, may also cause severe encephalitis and multi-organ failure. The reason for the aforementioned difficulties is due to the tendency of the virus to enter the bloodstream after infecting the lungs, the consequence of which will provide it with free access to every organ in the body. In the seven documented cases, four of them were declared clinically dead, ranging from 6 days (case #1) to up to 14 months (case #3) after the initial exposure to the virus. For the three who recovered, one of them developed neurological complications even after the onset of the disease (case #6). Fortunately, for the other two, they recovered without relapse and no evidence of viral latency (cases #2 and #4).
Currently, similar to the closely related Nipah virus, HeV does not have any cures. Furthermore, outside of supportive care, the disease does not have any effective treatments. However, in recent years, a subunit vaccine for horses has been created, thereby contributing to the reduction in zoonotic transmissions. Furthermore, a monoclonal antibody-based treatment for HeV is currently under development. For now, ribavirin and chloroquine are the main post-exposure treatments for the disease. Prevention through proper hygiene and adequate protection in areas where HeV has been reported remains the top priority in defending oneself against the virus.
