The flying fox fruit bat carries Nipah virus, which can be fatal in humans

Nick Baker www.ecologyasia.com

[DHAKA] Nipah virus has returned to Bangladesh for the fourth successive year, claiming at least 12 lives and infecting a further 32 people since it was first reported on 10 January.

According to Bangladesh's Department of Disease Control, the latest outbreak began in Tangail district, north of Dhaka, where 13 people developed a fever and became unconscious after drinking the juice of local palm fruits.

Researchers from the Dhaka-based Institute of Epidemiology, Disease Control and Research (IEDCR) suspected Nipah virus because last year's outbreak was caused by contact with fruit bats, which carry the virus and can transmit it to people.

The team thinks the juice was made from fruit contaminated by fruit bat droppings, or from fruit the bats had half-eaten.

The researchers sent samples of patients' blood to the Centers for Disease Control and Prevention in Atlanta, United States, which confirmed Nipah infection in one of them.

Bangladesh does not have adequate research facilities for diagnosing the virus or working on ways of controlling it. One constraint is that there are no laboratories in which the virus can be studied safely, without a risk of it escaping and infecting more people.

The IEDCR, however, is trying to find out how the outbreak began. Although the researchers suspect fruit bats are the main carriers of Nipah virus, they are also collecting samples of blood, tissue and droppings from other species — including cats, dogs, poultry, cattle and rodents — to see whether the virus has other hosts. By sampling fruit trees, they hope to determine whether the virus can be transmitted through contact with fruit touched by the bats.

Mahmudur Rahman, lead researcher and director of the IEDCR, told SciDev.Net that climate might also play a role in patterns of outbreaks, as each of the previous outbreaks also occurred in winter.

Strong evidence of human-to-human transmission of Nipah virus was found for the first time during last year's outbreak, according to research published in the Health and Science Bulletin of the Dhaka-based Centre for Health and Population Research.

Because of this threat, the Directorate of Health Services has advised healthcare officials to wear masks and gloves when treating patients suspected of having Nipah, and the public has been warned to avoid close contact with infected people.

Symptoms of Nipah virus infection are similar to those of influenza, such as fever and muscle pain. In some cases, inflammation of the brain occurs, leading to disorientation or coma. Around half of the symptomatic cases are fatal.

Rahman thinks there could be a connection between a recent increase in Bangladesh of cases of encephalitis, or inflammation of the brain, and Nipah or a Nipah-like virus. "We need extensive research on encephalitis," he says.

There is no cure for Nipah, but a vaccine is in development.

According to Bangladesh's Directorate of Health Services, Nipah virus has infected a total of 211 people and killed 59 of them since 2001, when the virus was first detected in the Bangladesh. The only previously reported outbreaks of Nipah occurred in Malaysia and Singapore between September 1998 and May 1999.

Link to full paper on human-to-human transmission of Nipah virus in Health and Science Bulletin

Reference: Health and Science Bulletin 2, 5 (2004)