1. What is Japanese Encephalitis?
Answer: Japanese Encephalitis viral infection is a mosquito-borne flavivirus disease that belongs to the same genus as West Nile virus, yellow fever, and dengue. The Japanese Encephalitis Virus (JEV) is responsible for the condition and is spread by an infected Culex tritaeniorhynchus mosquito. Other mosquitoes belonging to the Culex group, i.e., Culex vishnui and Culex pseudovishnui, are also the chief vectors for spreading the disease in India. Every year near to 68000 clinical cases of Japanese Encephalitis is recorded in many countries of Asia. The first outbreak of Japanese Encephalitis was documented in 1871 in Japan.

2. Which countries have frequent cases of Japanese Encephalitis?
Answer: According to the WHO, 24 countries of the South-East Asia and Western Pacific regions have a high risk of transmission of Japanese Encephalitis Transmission. Asian countries, including China, India, Indonesia, Japan, Malaysia, Myanmar, Nepal, Pakistan, Philippines, Republic of Korea, and Srilanka, have recorded many epidemics and sporadic cases of Japanese Encephalitis.
The disease has two Transmission patterns:

  • The first is the Sporadic pattern of transmission. This pattern is found all around the year in countries like Brunei, Malaysia, and Singapore. In Japan, the sporadic pattern is found from June to September. Similarly, South Korea has a sporadic transmission pattern from July to October.
  • The second is the Endemic/Hyperendemic pattern. Countries including Myanmar, Cambodia, Thailand, Vietnam, southern India, Laos, and Northern China have this transmission pattern from May to October. Countries like Bangladesh, Nepal, and parts of Northern India have this pattern from July to December.

3. How does Japanese Encephalitis spread?
Answer: Japanese Encephalitis viral infection does not spread from humans to humans. Humans are the dead-end host for the disease. This is because humans infected with the virus do not develop enough concentration of the JE virus in their bloodstream that can infect mosquitoes, unlike the cases in dengue and malaria.

The transmission cycle for the JE virus lies between mosquitoes and vertebrate hosts like pigs and water birds. When a mosquito sucks blood from a pig infected with the JE virus, the JE virus enters the mosquito’s body and gets it infected. When it bites a human, this infected mosquito transmits the JE virus inside the human body. Thus, humans are the incidental host for the JE virus.

4. How long is the incubation period for Japanese Encephalitis?
Answer: The incubation period, i.e., the time from infection till illness, is typically five to fifteen days.

5. What are the symptoms of Japanese Encephalitis?
Answer: The course of Japanese Encephalitis Disease is divided into three stages.
Stage 1: Prodromal Stage
Symptoms include:

  • High-grade fever
  • Severe Headache
  • Malaise
  • Nausea
  • Abdominal pain and vomiting in Children

Stage 2: Encephalitis Stage (the stage where CNS symptoms appear)
Symptoms include:

  • Altered sensorium (difficulty to think clearly and concentrate)
  • Convulsions (Involuntary contraction of muscles that leads to sudden irregular and violent movement of the body.)
  • Neck stiffness
  • Muscular Rigidity( muscular stiffness)/Movement disorders
  • Mask-like facies (expressionless face)
  • Abnormal Movements
  • Seizures in children
  • Spastic Paralysis
  • Behavioral Changes
  • Coma
  • A small number of cases in children showing clinical features of aseptic meningitis

Stage 3: Late Stage Noticeable by recovery or persistence signs of CNS injury
Death usually occurs due to CNS disorders that arise during the first week.

6. Who are at risk of getting Japanese Encephalitis?
Answer: The Japanese Encephalitis virus can infect a population of any age. However, the risk of infection in children is more than in adults. The ratio of infection among Children to that of adults is 200:1. Therefore, adults living in endemic regions would have a natural immunity to JEV if they had a previous infection from the virus during their childhood.

The risk factors of getting Japanese Encephalitis include:

  • People residing or traveling to urban or periurban Japanese Encephalitis endemic regions of South-East Asian countries and Western Pacific Regions.
    • People residing near paddy fields and involved in pig farming.
  • People and society that are not involved in keeping a clean environment lack the knowledge to stop the breeding and aggressive biting of the mosquitoes.
  • People who do not use mosquito nets during sleeping and do not wear proper clothes while traveling or residing in JE endemic countries.
  • Waterbirds that migrate from Japanese Encephalitis endemic countries are also a risk of spreading the JE virus.
  • Children under fifteen years of age living in endemic areas
  • Older people living in endemic areas

7. How is Japanese Encephalitis diagnosed?
Answer: The diagnostic methods used to diagnose Japanese Encephalitis include:

  • Japanese Encephalitis virus-specific Laboratory tests that use ELISA to capture the presence of IgG and IgM antibodies in a single sample of cerebrospinal fluid (CSF). The physician collects the cerebrospinal fluid by doing a lumbar puncture or spinal tap. The IgM antibodies specific to the Japanese Encephalitis virus can be found three to eight days after disease onset. However, antibodies can remain in the body between 30 and 90 days, or sometimes even longer.
  • Nucleic acid amplification test
  • Histology with immunohistochemistry
  • Virus culture of postmortem tissues
  • Simple nitrocellulose membrane-based format diagnostic technique
  • CT scan or MRI scan is also used.

8. What are the physical complications caused by the Japanese Encephalitis Virus in Children?
Answer: Children, who survive the disease, take time to regain the functions of their neurological systems and experience the following complications:

  • Slow speech
  • Difficulty in speaking
  • Partial Paralysis
  • Motor disturbance
  • Pneumonia
  • Urinary Tract Infection
  • Stasis Ulcers

9. How is Japanese Encephalitis treated?
Answer: There are no medications (antivirals) at present to treat Japanese Encephalitis viral infection. However, early diagnosis and supportive care can manage and help the patient’s early recovery. Supportive care includes hospitalization, proper rest, intravenous fluids, medication to reduce fever, and respiratory support.
Vaccines are available to create immunization against the JE virus. The vaccines are divided into four types:

  • Inactivated mouse brain-derived vaccines
  • Inactivated cell culture-derived vaccines
  • Live Attenuated vaccines
  • Live Recombinant vaccines

The vaccine available in the USA is under the brand name Ixiaro. It is given in the muscles and is a very-cell-derived inactivated vaccine.

10. Is there any Japanese Encephalitis vaccine in India?
Answer: In India, the Central Research Institute, Kasauli, has indigenously developed a Japanese Encephalitis vaccine derived from virus-infected mouse brains. Three doses are required to produce immunization. However, due to the limited production of vaccines using mouse brain technology, India has started developing Tissue Cultured vaccines (Vero-cell derived vaccines), which are feasible for mass production.
Jenvac by Bharat Biotech is currently India’s first indigenously Vero-cell derived vaccine developed in collaboration with the National Institute of Virology, India. The vaccine is a single dose vaccine containing inactivated Indian strain of the Japanese Encephalitis virus. It is safe and effective.

11. What are the preventive measures to stop Japanese Encephalitis infection?
Answer: Different methods to prevent the Japanese Encephalitis viral infection include:

  • Always keep your surroundings clean. Do not let garbage and stagnant water stay near your home. Make sure your house gets proper sunlight and is cleaned regularly.
  • Drainage pits should be appropriately covered and should not be clogged.
  • People in rural areas should limit their visits to paddy fields during the evening and stay away from pigs when there is no work. In addition, slaughterhouses involved in pig meat should keep their surrounding (both internal and external) clean.
  • It is advised to make a habit of wearing long sleeve shirts, full pants, and shoes while stepping out of your house during the evening and night.
  • Parents should ensure that babies and children are appropriately dressed to prevent mosquito bites.
  • Use mosquito repellent cream and always sleep under MOSQUITO nets.
  • Before taking any herbal medication or allopathic medication, or applying any topical creams to prevent or treat Japanese Encephalitis, always take advice from a medical practitioner.


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