How it began
During the 1998 to 1999 outbreak, Kaw Bing Chua was working in a laboratory at the University of Malaya. His superiors believed the cause was Japanese encephalitis virus, but Chua disagreed. He inoculated cell cultures with cerebrospinal fluid from a patient and saw syncytia form, which would not be expected of that virus. He took the isolate to the CDC in Fort Collins and then Atlanta, where it was shown to be a new virus related to Hendra virus. CSIRO dates the isolation to March 1999.
Before it existed
An outbreak of respiratory disease and encephalitis in pigs began in 1998 around Ipoh in Perak, followed by lethal encephalitis in people linked to pig farming. The pig disease was first attributed to classical swine fever and the human disease to Japanese encephalitis. Authorities sprayed against mosquitoes and vaccinated workers against Japanese encephalitis. Neither measure slowed the epidemic.
How it works
The virus is a paramyxovirus related to Hendra virus, which had been found in Australian horses in 1994. Antibodies to Hendra virus reacted with the Malaysian isolate. It was named after Kampung Sungai Nipah, home of the patient whose sample gave the first isolate. Later work found that the natural reservoir is fruit bats, and that pigs kept in orchards were infected by bat urine, feces or dropped fruit and passed the virus to people.
What changed first
The outbreak in Malaysia ended after 1.1 million pigs were culled, and disease among abattoir workers in Singapore stopped when pig imports from Malaysia were halted. A total of 283 human cases with 109 deaths was recorded. A review of the outbreak described a near collapse of the pig farming industry.
Where it stands today
No further infections of pigs were reported in Malaysia or Singapore after the first outbreak, which is attributed in part to better farm biosecurity. Outbreaks have since occurred in Bangladesh and India. There are no licensed vaccines or therapeutics, and the World Health Organization lists Nipah among viruses with potential to cause a public health emergency. A conference in Singapore in 2019 marked 20 years since the discovery.
