Epidemiology of henipavirus disease in humans.

All seven recognized human cases of Hendra virus (HeV) infection have occurred in Queensland, Australia. Recognized human infections have all resulted from a HeV infected horse that was unusually efficient in transmitting the virus and a person with a high exposure to infectious secretions. In the large outbreak in Malaysia where Nipah virus (NiV) was first identified, most human infections resulted from close contact with NiV infected pigs. Outbreak investigations in Bangladesh have identified drinking raw date palm sap as the most common pathway of NiV transmission from Pteropus bats to people, but person-to-person transmission of NiV has been repeatedly identified in Bangladesh and India. Although henipaviruses are not easily transmitted to people, these newly recognized, high mortality agents warrant continued scientific attention.