Nipah virus is a paramyxovirus, an RNA virus belonging to the genus Henipavirus which also includes Hendra virus (measles is a distant cousin). It is, according to Dr. Jonathan Epstein, who's been studying Nipah for 15 years, "the worst disease no one has ever heard of." It first spilled into humans in 1998, after it caused a massive outbreak in people and pigs in Malaysia which resulted in 265 cases, 105 deaths and the loss of millions of pigs as a result of outbreak control efforts. There is no known treatment for Nipah virus and its symptoms move quickly from headache and drowsiness to coma in a matter of days.
The outbreak in Malaysia began on a large-scale, industrialized pig farm that had fruit trees planted next to the pig enclosures. Giant fruit bats–which carry the virus and occasionally shed it, but are not affected by it–fed on mangoes in trees that overhung the pig pens and dropped bits of fruit contaminated with saliva, and occasionally nipah virus, into the pens where pigs were able to eat them. Farm workers became infected by pigs that developed severe respiratory disease and spread the virus by coughing. The movement of infected pigs throughout the country drove the outbreak until Malaysian health officials were able to stop its spread.
While Malaysia has not experienced an outbreak since that first spillover, Nipah virus outbreaks were later recognized in India and Bangladesh beginning in 2001 and cause nearly annual outbreaks in Bangladesh. In Bangladesh, Nipah virus is transmitted directly from bats to people via date palm sap, a sweet drink harvested and consumed across Bangladesh and in parts of India. People become infected when bats shedding Nipah virus contaminate the sap overnight with saliva or other excreta as they drink the sap. As with the outbreak in Malaysia, Nipah makes its way from bats into people or livestock through the contamination of food that is shared by people and bats.
With no treatment outside of supportive care, Nipah virus is one of the diseases shortlisted by the World Health Organization as a priority for research and study.
EcoHealth Alliance has been studying Nipah virus for 15 years and our experts advised WHO as they developed their list of the ten most important pathogens. One of our research priorities is to study Nipah virus in bats to determine where and when they are most likely to shed virus which could lead to a human outbreak. Ultimately, we want to be able to help focus limited public health resources to making sure that Nipah virus never becomes a global pandemic.