The 1998–1999 MalaysiaNipah virus outbreak was a Nipah virus outbreak occurred from September 1998 to May 1999 in the states of Perak, Negeri Sembilan and Selangor in Malaysia. A total of 265 cases of acute encephalitis with 105 deaths caused by the virus were reported in the three states throughout the outbreak. The Malaysian health authorities at the first thought Japanese encephalitis was the cause of infection which hampered the deployment of effective measures to prevent the spread before being finally identified by a local virologist from the Faculty of Medicine, University of Malaya that it was a newly discovered agent named Nipah virus. The disease was as deadly as the Ebola virus disease, but attacked the brain system instead of the blood vessels. University of Malaya's Faculty of Medicine and the University of Malaya Medical Centre played a major role in serving as a major referral centre for the outbreak, treating majority of the Nipah patients and was instrumental in isolating the novel virus and researched on its features. This emerging diseases where it caused major losses to both animal and human lives, affecting livestock trade and created a significant setback to the swine sector of the animal industry in Malaysia. The country also became the origin of the virus where it had no more cases since 1999 but further outbreaks continue to occur in Bangladesh and India.
Background
The virus firstly struck pig-farms in the suburb of Ipoh in Perak with the occurrence of respiratory illness and encephalitis among the pigs where it is firstly thought to be caused by Japanese encephalitis due to 4 serum samples from 28 infected humans in the area tested positive for JE-specific Immunoglobulin M which is also confirmed by the findings of World Health Organisation Collaborating Centre for Tropical Disease at the Nagasaki University. A total of 15 infected people died during the ensuing outbreak before the virus began to spread into Sikamat, Nipah River Village and Pelandok Hill in Negeri Sembilan when farmers affected by the control measures began to sell their infected pigs to these areas. This resulted 180 patients infected by the virus and 89 deaths. With further movement of the infected pigs, more cases emerged from around Sepang District and Sungai Buloh in Selangor with 11 cases and 1 death reported among abattoir workers in Singapore who had handled the infected pigs imported from Malaysia.
Authorities response and further investigation
Since the cause was firstly wrongly identified, early control measures such as mosquito foggings and vaccination of pigs against JE were deployed to the affected area which proved to be ineffective since more cases emerged despite the early measures. With the increasing deaths reported from the outbreak, this caused nationwide fear from the public and the near collapse of local pig-farming industry. Most healthcare workers who taking care of their infected patients had been convinced that the outbreak was not caused by JE since the disease affecting more adults than children including those who had been early vaccinated against JE. Through further autopsies on the deceased, the findings were inconsistent from the earlier results where they suggest it may come from another agent. This was supported with several reasons such as all of the infected victims had a direct physical contacts with pigs and all of the infected pigs had developed severe symptom of barking cough before it died. Despite the evidence gathered from autopsies results with new findings among local researchers, the federal government especially the health authorities insist that it was solely caused by JE which delayed further appropriate action taken for the outbreak control.
In early March 1999, a local medical virologist at the University of Malaya named Kaw Bing Chua finally found the root cause of the infection. Through his findings, the infection was indeed caused by a new agent named Nipah virus, taken from the investigation area name of Nipah River Village, where it is still unknown to available science records at the time. The virus origin is identified from a native fruit bat species. Together with the Hendra virus, the novel virus is subsequently recognised as a new genus, Henipavirus in the Paramyxoviridae family. He found that NiV and HeV shared enough epitopes for HeV antigens to be used in a prototype serological test for NiV antibodies which helped in the subsequent screening and diagnosis of NiV infection. Following the findings, widespread surveillance of pig populations together with the culling of over a million pigs was undertaken and the last human fatality occurred on 27 May 1999. The outbreak in neighbouring Singapore also ended with immediate prohibition of pigs importation to the country and their subsequent closure of abattoirs. The virus discovery received the attention from the AmericanCenters for Disease Control and Prevention, Commonwealth Scientific and Industrial Research Organisation and Singapore General Hospital who giving swift assistance towards the characterisation of the virus and the development of surveillance and control measures.
Aftermath
Until 2010s, the pig farming ban on Pelandok Hill was still in force to prevent the recurrence of the outbreak despite some people had quietly restarted the business after being instigated by community leaders. Most of the surviving pig farmers have turned to palm oil and Artocarpus integer cultivation. Since the virus has been named Nipah from the sample taken in Nipah River Village of Pelandok Hill, the latter area has become synonyms with the deadly virus.
Memorials
In 2018, the outbreak are being memorialised in a newly constructed museum named Nipah River Time Tunnel Museum in the Nipah River Village with several of the surviving victims stories have been filmed in a documentary which will be featured at the museum.
