What you need to know: The deadly Japanese Encephalitis explained

1. What is Japanese Encephalitis?
  • Japanese Encephalitis* (JE) is a deadly disease predominantly affecting the brain.
  • It is acquired from mosquito bites.
  • JE is the most common cause of viral encephalitis in Asia.
  • JE belongs to the same genus as dengue, yellow fever, and West Nile viruses

*Encephalitis is the inflammation of the brain caused by either a viral infection (JE, West Nile virus) or our own immune system mistakenly attacking brain tissues.

2. What’s the difference between the JE mosquito and dengue mosquito?
Dengue mosquito. Photo: iguadala.cat                       JE mosquito Photo: dreamtimes.com
  • Dengue is carried by the Aedes aegypti mosquito which originated from Africa. It is commonly identified with white markings in the legs.
  • Only the female Aedes mosquito can infect dengue to humans. This mosquito is also the carrier of yellow fever and Zika virus, among others.
  • Culex tritaeniorhynchus, a native of North Asia, is the carrier of JE. Like the dengue mosquito, only females can pass the virus.
  • Culex can be identified as yellowish to brown with stripes in the body.
3. How is it transmitted?
  • The virus can only be transmitted to humans by infected mosquitoes through a bite.
  • Other animals with the virus cannot transmit it to humans.
4. Where did it start? What is its history?
Southeast Asian countries. Photo: conceptdraw.com
  • The first case was recorded in Japan as early as 1871. No other detail was provided.
  • Biggest case was in 1924, still in Japan, with more than 6,000 cases wherein more than 50% died.
  • JE was principally present in rural areas of Japan, Korea, and China in the earlier 20th century.
  • However, cases have been more apparent in Southeast Asia, India, and Sri Lanka in the past three decades.
5. Who are at risk?
Filipino children. Photo: Ed Davad/Pixabay
  • Those who live in agricultural and rural areas are more at risk of acquiring JE.
  • JE mosquitoes live in agricultural and rural areas. Their larvae breed in pools of water e.g. flooded rice fields.
  • Children are most likely to be at risk of being infected.
6. Why are children more at risk?
  • Children, given their still-developing and weak immune systems, are more likely to be infected.
  • Adults tend to be immune as they get older.
7. Who or what are other risks?
Photo: thrombocyte.com
  1. Pregnant women
  2. Those who smell of sweat
  3. People with blood type O
  4. Wearing dark clothing
8. Are there early signs?
Photo: The Asian Parent Singapore
  • Fever and headache will occur to a person with mild JE, but these can develop quickly to swelling of the brain in a span of 5 to fifteen days.
9. What are the symptoms for those with severe JE infections?
  1. Headache
  2. High fever
  3. Tremors or involuntary movement of the muscles
  4. Nausea and vomiting
  5. Stiff neck
  6. Spastic paralysis
  7. Convulsions
  8. Swelling of the testicles
  9. Signs of altered mental status e.g. near unconsciousness, disorientation, coma
10. What happens when you have JE?
  • JE affects the brain or the whole nervous system. Given that, coma, disorientation, limited physical movement, unconsciousness, confusion may occur to those with sever JE.
11. What is the mortality rate or death rate?
  • Around 20% to 30% of the victims die.
12. What happens if you survive JE?
  • Of those who survive, 20% to 30% suffer permanent intellectual, behavioral or neurological problems such as paralysis, recurrent seizures or the inability to speak.
13. Is there a cure for this? How can it be prevented?
Photo: dfuhlert/Pixabay
  • Unfortunately, there is not a known cure for JE.
  • But, it can be prevented through World Health Organization-approved vaccines.
  • There are 4 main types of JE vaccines currently in us (nactivated mouse brain-derived vaccines, inactivated Vero cell-derived vaccines, live attenuated vaccines, and live recombinant vaccines).


Photo: Matador Network
When was the first recorded JE case in the Philippines?
  • The first recorded case of JE in the Philippines was in the 1950s.
How many are infected nationwide? And how many have died?
  • From January 1 to August 26 this year, there have been 133 patients and 53 cases nationwide.
  • 9 deaths have been reported – 4 from Pampanga; 2 from Zambales; and 1 each from Laguna, Nueva Ecija, and Pangasinan
Why is it predominant in Central Luzon?
Photo: University of Reading Weblogs
  • It was mentioned that JE mosquitoes live in rice fields and agricultural areas. Central Luzon houses the most rice fields in the country as it is the largest producer of rice in the country.
What are the prevention methods available in the Philippines?
  • Vaccines are available in hospitals for P2,000 to P4,000 per shot.
  • In the Philippines, the only available brand of the vaccine at present is the Imojev, which is being supplied by pharmaceutical company, Sanofi Pasteur.
Current and future plans of the Department of Health (DOH)?
Department of Health Secretary Jean Paulyn Rosell-Ubial. Photo: UNTV
  • DOH plans to recommend the JE vaccine for inclusion in the national immunization program of the country in 2018.

SOURCES: 1, 2, 3, 4, 5, 6, 7