1998–1999 Malaysia Nipah virus outbreak

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 was initially believed to have been caused by Japanese encephalitis (JE), due to four serum samples from 28 infected humans in the area which tested positive for JE-specific Immunoglobulin M (IgM) which is also confirmed by the findings of the World Health Organization (WHO) Collaborating Centre for Tropical Disease at 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 impacted 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 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. ==Response and further investigation==

Since the cause was initially 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, with more cases emerging despite these early measures. where it was unknown in available scientific records at the time. The virus origin was determined to be from a native fruit bat species. Together with the Hendra virus (HeV), the novel virus was subsequently recognised as a new genus, Henipavirus (Hendra + Nipah) in the Paramyxoviridae family. 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 pig importation to the country and the subsequent closure of abattoirs. The virus discovery received the attention from the American Centers for Disease Control and Prevention (CDC), Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Singapore General Hospital (SGH) which gave swift assistance towards the characterisation of the virus and the development of surveillance and control measures. ==Aftermath==

Until the 2010s, the pig farming ban on Pelandok Hill was still in force to prevent the recurrence of the outbreak, despite some farmers having quietly restarted their businesses after being encouraged by community leaders. Most of the surviving pig farmers have turned to palm oil and Artocarpus integer (cempedak) 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. In a response from the Singapore's government, its country's food agency, Agri-Food and Veterinary Authority of Singapore (now Singapore Food Agency (SFA)), banned the exports of pig blood curd in 1999. The ban has since been lifted after 27 years on 1 April 2026, with the pig blood curd imports from Thailand requiring approval from SFA beforehand. Before the ban was lifted, one seller was prosecuted for selling imported pig blood curd online in 2021. ==See also==