Japanese encephalitis – Symptoms, Treatments, and more

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Japanese encephalitis

Japanese encephalitis is a mosquito-borne disease which is caused by a single-stranded RNA virus. Encephalitis infection means inflammation in the brain, which can lead to headaches, fever and seizures along with other range of symptoms.

According to CDC (Centre for Disease Control and Prevention), fewer than 1% of people affected with the disease develop symptoms.

Japanese encephalitis virus belongs to the Flavivirus family. Mosquitoes act as a vector that passes on the infection.

Japanese encephalitis is one of the most common infections in Asia and Australia. The Culex mosquitoes are responsible for passing on the infection. The infection can be commonly seen in agricultural areas like farms, where mosquitoes are profoundly found.

However, the transmission can occur in other urban areas too. In most cases, the infection remains asymptomatic, and patients who show symptoms can suffer from significant morbidity and mortality.

According to an NCBI source, children are commonly prone to the infection and people who live in the endemic area can develop herd immunity as they grow as adults.

Currently, there is no specific treatment for Japanese encephalitis. There are vaccines available for children to prevent the infection. However, the best prevention is to protect yourself from mosquito bites.

According to NCBI, the virus amplifies in intermediate hosts like birds and pigs as they are found abundantly in farms and agricultural lands. The agricultural lands also attract a lot of birds and other cattle. So, this can be a reason for animals being the first point of contact for the infection.

According to the National Library of Medicine, humans are considered to be the dead-end host as the virus does not generally develop high levels in humans to pass on the virus to the feeding mosquitoes.

However, the infection is being reported in countries like China, Singapore and Taiwan. When travellers visit these highly infectious endemic areas, they are advised to vaccinate themselves from getting infected with Japanese encephalitis.

In most cases, the infection passes from mosquitoes. There are concerns that exposure to amplifying hosts like pigs can transmit the virus when being in close contact with vector involvement.

Who is at risk?

People who live in the endemic area are commonly prone to infection. It is also reported that people who work in agricultural lands or work near pigs infected with the virus are also at an increased risk of getting infected.

However, the direct risk of infection is when people are bitten by mosquitoes.

Additionally, people who live in tropical regions are also prone to Japanese encephalitis. During the rainy season, the population of mosquitoes can increase, as a result of which the infection rate increases.

Signs and symptoms of Japanese encephalitis

In most cases, the symptoms of the Japanese encephalitis virus will not show any symptoms. However, people with the infection will develop symptoms from 5-15 days from the onset of the infection.

  • During the initial days of infection, there will be symptoms like fever, vomiting and headache.
  • Neurological symptoms like confusion, weakness, movement disorders and lack of concentration.
  • According to CDC, people affected with Japanese encephalitis have a mortality rate of 20-30%.
  • However, after recovery from Japanese encephalitis, there is an increased chance of people living with a permanent disability.

Diagnostic Testing for Japanese encephalitis

The diagnosis of Japanese encephalitis involves a laboratory test to confirm the case of Japanese encephalitis and rule out the infection of encephalitis.

According to WHO, the recommended diagnostic method is to test for the specific antibody JEV-specific IgM presence in the cerebrospinal fluid using ELISA.

The cerebrospinal fluid sample testing is used to reduce the cases of false positivity. Other diagnostic methods include and neuroimaging like MRI, CT scan.

In fatal cases, histopathology, immunohistochemistry and nucleic acid amplification test are recommended.

Treatment for Japanese encephalitis

There is no specific treatment for Japanese encephalitis. There are vaccines available for the disease to control the infection.

The treatment is supportive with certain anti-inflammatory and pressure reducing agents, rest and hydration management.

Maintaining a proper airway is crucial for recovery in people with significant symptoms.

Additionally, nutritional therapy and electrolyte therapy is required to stabilise a patient who is severely ill. Medications for the resulting symptoms and signs play a major role in the recovery from the infection. In severe cases, intensive care treatment is required.

Japanese encephalitis outcome

Managing Japanese encephalitis requires a multidisciplinary approach. Currently, there is no standard antiviral for the infection. So, the patients might require support from various specialists such as intensive care specialists, respiratory physicians, infectious disease specialists, Neurologists, Nutritionists, Physical and rehabilitation medicine, etc.

The best way to protect yourself from the infection is to avoid bites from mosquitoes. Recovery from the infection can occur for months with or without permanent neurological damage.

Vaccines for Japanese encephalitis

Japanese encephalitis vaccine is an inactivated vaccine. Inactivated vaccine means the virulence of the virus is completely or partially altered to make it effective and safe.

The inactivated vaccine usually contains virus particles or genetic material to activate the immune system of the body.

How to prevent Japanese encephalitis?

Prevention is better than cure. So, prevent yourself from getting bit by mosquitoes. Mosquitoes can bite during the day and the night. Use insect repellents and wear long sleeve dresses to avoid getting bit by insects. If you are travelling to highly infectious places, make sure you get yourself vaccinated.

According to CDC, the presence of some insect repellents are safe and effective for pregnant and breastfeeding women.

To protect children from Japanese encephalitis infection, follow these basic techniques.

  • You can use mosquito nets to protect the baby against mosquitoes when they sleep.
  • Choose the dress for your baby in such a way that the baby’s legs and hands are covered.
  • Before using insect repellent on children, it is important to consult your doctor.
  • Keep your surroundings free from stagnant water as mosquitoes lay eggs in these water resources. If there are mosquito eggs, make sure you destroy them or inform your mosquito control.
  • Also, check for containers that hold water, like flowerpots, trash containers, planters, pools, bathtubs, buckets and tires. Make sure you check them for stagnant water once a week to stop mosquitoes from laying eggs.


Japanese encephalitis is commonly prevalent in tropical areas, where mosquitoes can breed easily.

According to World Health Organisation (WHO), a Japanese encephalitis outbreak can occur every 2-15 years. The transmission of infection from mosquitoes can occur during the rainy season, and there are chances of intensification.

The spread of the infection to new areas is reported to be agricultural and farmlands, where water stagnation is commonly reported.


How soon do people get sick after being bitten by an infected mosquito

The onset of infection can occur within 3-14 days of the mosquito bite that has been infected with the virus.

Where does Japanese encephalitis occur?

The most commonly reported areas of Japanese encephalitis are—Common parts of South East Asia, the Pacific Islands and the far East.

Who should get the Japanese encephalitis vaccine?

Japanese encephalitis vaccine is recommended for people who live in the endemic areas and travellers who plan to visit the endemic area for a short period of time.

What are the side effects of Japanese encephalitis vaccination?

According to CDC, the most common side effects of Japanese encephalitis vaccination are tenderness, swelling, pain and redness in the injection site.


The Information including but not limited to text, graphics, images and other material contained on this blog are intended for education and awareness only. No material on this blog is intended to be a substitute for professional medical help including diagnosis or treatment. It is always advisable to consult medical professional before relying on the content. Neither the Author nor Star Health and Allied Insurance Co. Ltd accepts any responsibility for any potential risk to any visitor/reader.

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