Background
The Japanese Encephalitis virus (Flaviviridae virus) is endemic to most Asian countries and occurs throughout the year in pigs although it is not normally transmitted to humans. However, JE is noted as the leading cause of viral encephalitis in Asia with 30, 000 to 50,000 cases reported annually throughout the region and nine to 91 annual cases in Malaysia.
The virus outbreak in 1998 to 1999 spread quickly from the epicentre at Kinta Valley, Perak to some 250 km south in Sikamat and Bukit Pelanduk areas in Negri Sembilan. By 2 April 1999, there were 69 deaths in Malaysia with the majority in Bukit Pelanduk area and one death in Singapore with seven other abattoir workers in Singapore admitted for symptoms and observation at Tan Tock Seng Hospital.
Unlike most JE outbreaks in Malaysia in 1998 -1999, this occurred amongst adult workers when normally it infects children, thus suggesting the presence of another virus. Some suggest this unknown virus was a Hendra-like parallel, later called the Nipah virus.
Testing at the Centres for Disease Control and Prevention (CDC) in Atlanta showed that victims in Singapore were infected by the Nipah virus, similar to that which led to an outbreak in Australia in 1994 and 1995 amongst humans and horses. The virus was initially thought to be the Japanese Encephalitis which had previously wrecked havoc in the pig industry in Malaysia. The JE virus is spread via a Culex breed of mosquitoes. However, the Nipah virus is thought to have been transmitted to humans through infected pigs and is not believed to be communicable between humans.
Timeline
25 January 1999 : Primary Production Department (PPD) banned imports from one farm in Sikamat
3 March 1999 : PPD banned imports from all farms in Negeri Sembilan and Perak's Kinta Valley
18 March 1999 : Imports from all farms in Johor are banned
19 March 1999 : Banned all imports of all live pigs and closed the two abbatoirs for disinfection
26 April 1999 : Resume importing pigs from Indonesia
28 April 1999 : Wet markets to sell pork after the pigs from the Indonesia's Pulau Bulan was declared free from the Nipah virus. Pork is to be sold chilled instead of at room temperature
Impact
More than 200 developed symptoms with 28 deaths in Malaysia whilst eleven were infected in Singapore out of which one died. Both Singapore abattoirs were closed over five days and underwent an intensive disinfecting process. The animals were instead slaughtered at a new abattoir in Jurong which was equipped to chill the meat to between zero and four degrees Celsius. The fortunes of pig farmers in Malaysia were severely affected. Singapore, which imported at least 80% of its pork supply from its neighbour, began to restrict orders. At least 1 million pigs were culled. Many pig farmers went bankrupt. With effect from 1 November 1999, all pork meat on sale had to be placed in display chillers. Singapore hawkers and retailers turned to chicken as an alternative causing an increase in the price of poultry. Chicken variations of popular dishes like the famed barbecue pork, charsiew, appeared.
Japanese Encephalitis
Description : The virus is transmitted via a particular breed of Culex mosquitoes (Culex tritaeniorhnychus)
Symptoms : Flu-like symptoms such as headaches, fever and feelings of weakness. Vomiting and delirium may follow. The infection may then progress to an inflammation of the brain which causes permanent disability and finally death.
Cure : There is no cure to the virus although a vaccine has been developed. The vaccine however reportedly causes serious allergic side effects in some recipients.
Prevention : Although there is no clear way of preventing the disease, precautions include reducing exposure to mosquitoes.
Nipah Virus
Description : Member of the Paramyxovirus family. It is unknown how the virus is transmitted but it is believed to be passed on from live pig to humans and not communicated between humans. Named the Nipah virus or Nipah encephalitis.
Prevention : Cleaning extensively with soap, detergent or disinfectants is believed to kill the virus. Immunisation against Japanese encephalitis did not prevent infections from this virus.
Author
Edian Azrah Bte Kamaron
References
Anatomy of a crisis. (1999, March 27). The Straits Times.
Dangerous Culex species rare here. (1999, March 24). The Straits Times.
Nathan, D. (1999, March 24). Singapore: Spread of pig virus halted, says PPD. The Straits Times.
11 blood samples have Hendra-like virus. (1999, March 31). The Business Times.
Wet markets to start selling pork next week. (1999, April 24). The Business Times.
What is Encephalitis?. (1999, March 21). The Straits Times.
BBC MMIV. (n.d.). Japanese Encephalitis. Retrieved August 22, 2002, from news.bbc.co.uk/1/hi/health/medical_notes/307709.stm
Centers for Disease Control and Prevention. (2003). CDC Japanese Encephalitis home page. Retrieved December 31, 2004, from www.cdc.gov/ncidod/dvbid/jencephalitis/index.htm
Ministry of Foreign Affairs, Japan. (1995-2004). Emergency aid to Malaysia for responding to the outbreak of Japanese Encephalitis. Retrieved December 31, 2004, from www.infojapan.org/announce/announce/1999/4/406-3.html
World Health Organization. (2004). Disease oubreak reported: Hendra-like virus in Malaysia and Singapore. Retrieved December 31, 2004, from www.who.int/disease-outbreak-news/n1999/apr/n07aapr1999.html
Further Readings
MMWR. (n.d.). Outbreak of Hendra-like virus - Malaysia and Singapore, 1998 - 1999. Retrieved July 7, 2003, from
www.cdc.gov/epo/mmwr/preview/mmwrhtml/00056866.htm
Pig Disease Information Centre. (2001-2004). Nipah virus epidemic. Retrieved December 31, 2004, from
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.
