Wildlife Trust's Consortium for Conservation Medicine
reports that the World Health Organization (WHO) has now confirmed two recent outbreaks in humans of deadly Nipah virus in Bangladesh. The Consortium has been researching the origins of Nipah virus under a grant from the National Institutes of Health.
Previously, Nipah virus has only been confirmed in Malaysia, where a 1999 outbreak killed an alarming 40% of those infected.
WHO reports that in February 2004, an outbreak of Nipah virus spread across six districts of Bangladesh and claimed 17 human deaths out of 23 cases - a mortality rate of 74%. A second outbreak in the Faridpur district killed 18 of a total 30 cases - a 60% mortality rate - as of April 19th. Common signs of infection include flu-like symptoms (fever, headache, vomiting), seizures, loss of consciousness, and coma.
Wildlife Trust President Dr. Mary Pearl says, "The reappearance of SARS in China and the identification of Nipah virus in Bangladesh, following its emergence in Malaysia, are serious warnings. The current state of understanding of lethal disease agents that move from one species to another, and then to humans in crowded landscapes is woefully inadequate. People must recognize that disease emergence is yet another potential consequence of ecosystem disruptions."
In Malaysia, the 1999 outbreak has been attributed to fruit bats finding new sources of food in fruit trees planted on one of Malaysia's largest pig farms. The pigs most likely became infected by eating infected fruit dropped into the pig stalls by bats from overhanging trees, and then passed the infection on to humans.
This year in Bangladesh, giant fruit bats are also suspected to be the reservoir for Nipah virus. (In Australia, they are suspected to be the reservoir of a related virus, Hendra virus. Both Hendra and Nipah viruses have been classed within the new genus "Henipavirus".)
The outbreaks in Bangladesh appear to be different from those in Malaysia because no intermediate animal host (i.e., pigs) has yet been identified. The current outbreak includes a number of victims under age 19. It was noted that young boys collected and ate fruits in the trees before dawn. This observation has given rise to the hypothesis that infection could have occurred from eating the same fruits that fruit bats fed on during the night. Additionally, many of the cases in Bangladesh have occurred within households - with victims having had no direct contact with animals or bats. Human-to-human transmission, which did not play a significant role in the Malaysian outbreak, could therefore be possible in Bangladesh - which could lead to a greater number of cases.
Details of the Bangladesh outbreaks were reported in WHO's Weekly Epidemiological Record of April 23rd and can be found at: http://www.who.int/wer/2004/wer7917/en/.