Nipah virus outbreak (1999)



In March 1999, an abattoir worker in Singapore fell victim to what was initially thought to be the Japanese encephalitis (JE) virus but was subsequently verified as a yet unnamed Hendra-like virus (later known as the Nipah virus).1

Background
The virus outbreak began in late September 1998 in Malaysia. It had spread quickly from the epicentre at Kinta Valley in Perak to some 250 km south in the Sikamat and Bukit Pelanduk areas in Negri Sembilan.2 By April 1999, there were 103 deaths in Malaysia and one in Singapore. The victim in Singapore had died on 19 March.3

The outbreak in Singapore was initially thought to be caused by the JE virus, which is spread by the Culex mosquito. The JE virus is the leading cause of viral encephalitis in Asia, with an estimated 68,000 clinical cases reported annually. It is a mosquito-borne flavivirus related to dengue, yellow fever and West Nile viruses.4

However, the outbreak in Malaysia occurred among adults who had close contact with swine, therefore suggesting the presence of another virus.5 As such, Singapore took immediate measures to prevent its introduction to Singapore, including the suspension of live pig imports from affected farms in Malaysia, increasing the frequency of fogging as well as the spraying of larvicides to destroy the mosquitoes.6 All abattoir workers and pig traders in Singapore were also ordered to go for checkups.7

Tissue samples from three victims in Singapore, who had earlier tested negative for JE, were sent to the Centres for Disease Control and Prevention (CDC) in Atlanta, United States, for Hendra virus tests.8 Test results confirmed that JE was not involved. Instead 11 of the 15 blood samples from Singapore were found to be infected by a virus that is similar to the Hendra virus responsible for an outbreak in Australia in 1994 that had claimed the lives of some humans and horses. This Hendra-like virus  – found to be similar to that detected in Malaysia – was transmitted by infected pigs to humans and is not believed to be communicable between humans.9 The virus was later named the Nipah virus after the location where it was first detected in Kampung Sungai Nipah, Malaysia.10

Impact
Eleven people in Singapore were infected with the Hendra-like virus in March 1999, with one fatality.11 Both abattoirs at Jurong and Kim Chuan were closed over five days for disinfection after the Malaysian media first reported the possibility of a Hendra-like virus.12 Singapore subsequently banned imports from all farms in Negri Sembilan, Perak and north of Johor.13 The Malaysian authorities also culled 1.1 million pigs.14

After the ban on live pig imports was lifted, the animals were slaughtered at a new abattoir in Jurong, which was equipped to chill the meat to between zero and four degrees Celsius.15 With effect from 1 November 1999, all pork meat on sale had to be placed in display chillers.16 

Japanese encephalitis virus
Transmission: The virus is transmitted via a particular species of Culex mosquito, Culex tritaeniorhnychus.17

Symptoms: Incubation period is typically 5–15 days, with initial symptoms such as headache, fever and vomiting. Severe symptoms include mental status changes, neurologic symptoms, weakness and movement disorders. Fatality rate is about 20 to 30 percent, and among those who survive, 30 to 50 percent continue to have neurologic, cognitive or psychiatric symptoms.18
Treatment: Treatment is limited to  supportive care. Victims are usually hospitalised, and are advised to rest and take plenty of fluids as well as medicine to relieve fever.19
Prevention: JE vaccine is available and recommended for those who are travelling to endemic areas for more than a month. Other precautions include reducing exposure to mosquitoes.20

Nipah virus
Transmission: Member of the Paramyxoviridae family. Transmission of the virus to humans may occur from direct exposure to infected bats, infected pigs or infected people.21

Symptoms: Infection is associated with inflammation of the brain. Incubation period is 5–14 days, with signs of fever, headache, drowsiness, disorientation and mental confusion. Symptoms may progress to coma.22
Treatment: Treatment is limited to supportive care. Standard infection control practices and barrier nursing techniques should be adopted to prevent human-to-human transmissions.23
Prevention: Precautions include avoiding exposure to sick pigs and bats in endemic areas, and increased efforts in early detection of the disease and raising the awareness of transmission and symptoms.24



Author
Edian Azrah Bte Kamaron 



References
1. Ministry of Health Singapore. (1999). State of health: The report of the director of medical services. Singapore: Ministry of Health, p. 20. (Call no.: RSING 614.095957 SMH)
2. Wong, D. (1999, March 27). Outbreak. The Straits Times, p. 40. Retrieved from NewspaperSG; Centers for Disease Control and Prevention. (1999, April 9). Outbreak of Hendra-like virus - Malaysia and Singapore, 1998–1999. Morbidity and Mortality Weekly Report (MMWR), 48(13). Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/mmwr/preview/mmwrhtml/00056866.htm
3. Puah, P. (2006). The unknown killer: Understanding the Nipah outbreak in Malaysia. In S. V. Rengam & A. A. Choudry (Eds.), Appetite for destruction (pp. 69–90). Penang, Malaysia: Pesticide Action Network Asia and the Pacific, p. 73. (Call no.: RSEA 630.95 APP); Lim, A., & Yeo, G. (1999, March 21). Checkups for pig workers. The Straits Times, p. 1. Retrieved from NewspaperSG.
4 World Health Organization. (2017). Japanese encephalitis. Retrieved 2017, June 19 from the World Health Organization website: http://www.who.int/mediacentre/factsheets/fs386/en/
5. Centers for Disease Control and Prevention. (1999, April 9). Outbreak of Hendra-like virus - Malaysia and Singapore, 1998–1999. Morbidity and Mortality Weekly Report (MMWR), 48(13). Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/mmwr/preview/mmwrhtml/00056866.htm; Centers for Disease Control and Prevention. (2015, August 5). Transmission of Japanese encephalitis virus. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/japaneseencephalitis/transmission/index.html
6. Nathan, D. (1999, March 24). Dangerous Culex species rare hereThe Straits Times, p. 38. Retrieved from NewspaperSG.
7. Lim, A., & Yeo, G. (1999, March 21). Checkups for pig workers. The Straits Times, p. 1. Retrieved from NewspaperSG.
8. Lim, A., & Yeo, G. (1999, March 21). Checkups for pig workers. The Straits Times, p. 1. Retrieved from NewspaperSG.
9. 11 blood samples have Hendra-like virus. (1999, March 31). The Business Times, p. 2. Retrieved from NewspaperSG.
10. Puah, P. (2006). The unknown killer: Understanding the Nipah outbreak in Malaysia. In S. V. Rengam & A. A. Choudry (Eds.), Appetite for destruction (pp. 69–90). Penang, Malaysia: Pesticide Action Network Asia and the Pacific, p. 72. (Call no.: RSEA 630.95 APP); World Health Organization. (2017). Nipah virus (NiV) infection. Retrieved 2017, June 14 from the World Health Organization website: http://www.who.int/csr/disease/nipah/en/
11. Ministry of Health Singapore. (1999). State of health: The report of the director of medical services. Singapore: Ministry of Health, p. 20. (Call no.: RSING 614.095957 SMH)
12. Nathan, D. (1999, March 24). Spread of pig virus halted, says PPDThe Straits Times, p. 4; Nathan, D. (1999, March 25). Abattoirs’ reopening: Decision in two weeks. The Straits Times, p. 25. Retrieved from NewspaperSG.
13. Lim, A. (1999, March 19). Imports of pigs curbed as precaution. The Straits Times, p. 1. Retrieved from NewspaperSG.
14. Puah, P. (2006). The unknown killer: understanding the Nipah outbreak in Malaysia. In S. V. Rengam & A. A. Choudry (Ed.), Appetite for destruction (pp. 69–90). Penang, Malaysia: Pesticide Action Network Asia and the Pacific, p. 78. (Call no.: RSEA 630.95 APP)
15. Nathan, D. (1999, April 24). Ban on pig imports lifted. The Straits Times, p. 1. Retrieved from NewspaperSG.
16. Wet markets to start selling pork next week. (1999, April 24). The Business Times, p. 2. Retrieved from NewspaperSG.
17. Centers for Disease Control and Prevention. (2015, August 5). Transmission of Japanese encephalitis virus. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/japaneseencephalitis/transmission/index.html
18. Centers for Disease Control and Prevention. (2015, August 5). Symptoms & treatment. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/japaneseencephalitis/symptoms/index.html
19. Centers for Disease Control and Prevention. (2015, August 5). Symptoms & treatment. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/japaneseencephalitis/symptoms/index.html
20. Centers for Disease Control and Prevention. (2015, August 5). Prevention. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/japaneseencephalitis/prevention/index.html
21. Centers for Disease Control and Prevention. (2014, March 20). Transmission. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/vhf/nipah/transmission/index.html
22. Centers for Disease Control and Prevention. (2014, March 20). Signs and symptoms. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/vhf/nipah/symptoms/index.html
23. Centers for Disease Control and Prevention. (2014, March 20). Treatment. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/vhf/nipah/treatment/index.html
24. Centers for Disease Control and Prevention. (2014, March 20). Prevention. Retrieved 2017, June 14 from Centers for Disease Control and Prevention website: https://www.cdc.gov/vhf/nipah/prevention/index.html



Further resources
Pig Disease Information Centre. (2001–2004). Nipah virus epidemic. Retrieved December 31, 2004, from Pig Disease Information Centre website: www.pighealth.com/News99/NIPAH.HTM

Vadivale, M. (n.d.). Japanese Encephalitis. Retrieved July 7, 2003, from www.vadscorner.com/je.html



The information in this article is valid as at 2002 and correct as far as we are able to ascertain from our sources. It is not intended to be an exhaustive or complete history of the subject. Please contact the Library for further reading materials on the topic.
 

Subject
Public health
Epidemics--Singapore
Japanese Encephalitis Outbreak, Singapore, 1999
Public health--Singapore
Accidents
Swine--Diseases--Malaysia
Health and medicine>>Diseases>>Communicable diseases
Events>>Disasters
Politics and Government>>Health