A rash of encephalitis cases caused by Nipah virus in Malaysia between September 1998 and June 1999 killed more than a third of the victims, researchers there report.
The newly discovered virus belongs to the paramyxovirus group. Although one person caught the virus from an infected dog, in nearly all cases, the illness spread from pigs to people working on pig farms, says Chong Tin Tan, a neurologist at the University of Malaysia in Kuala Lumpur. Pigs that have the virus die, Tan reports.
Originally, however, the virus may have come from bats, he suggests. A related virus called Hendra is carried by fruit bats, also known as flying foxes. Highway construction in northern Malaysia could have uprooted bats from their native roosts and driven them into close proximity to the pig farms where the Nipah outbreaks occurred, Tan says.
"The high density of pig farms in the epidemic area contributed to the rapid spread of the disease," he says.