Japanese Encephalitis

Japanese Encephalitis

Japanese encephalitis(JE) is a viral disease that infects animals and humans. It is transmitted by mosquitoes in humans causing inflammation of the membranes around the brain. Japanese encephalitis is a leading cause of viral encephalitis in Asia generally spread from western pacific region in east to Pakistan in west and from Korea in north to Papua New Guinea in south.

Japanese encephalitis is a disease caused by a flavi virus that affects the membranes around the brain. Generally infections caused by Japanese encephalitis virus are mild (fever and headache) or without apparent symptoms, but sometimes 1 in 200 infections can result in severe disease characterized by rapid onset of high grade fever, headache, neck stiffness, disorientation, coma, seizures, spastic paralysis and death.


Japanese encephalitis has an incubation period of 5 to 15 days and the majority of infections are asymptomatic i.e. only 1 in 250 infections develop into encephalitis.

Intial symptoms include:

A high temperature (fever) of 38C (100.4F) or above
Feeling sick
Muscle pain
In rare cases, these initial symptoms last for a few days and then develop into serious symptoms:

Seizures (fits)
Changes in mental state, which can range from mild confusion to being very agitated or falling into a coma
Uncontrollable shaking of body parts (tremor)
Losing the ability to speak
Muscle weakness
Abnormally tense muscles (hypertonia)
Movement problems, such as shaking, stiffness, slowness of movement or paralysis
Difficulties in controlling the movements of the eyes
Difficulties in controlling the muscles of the face


Japanese encephalitis is caused by a flavi virus. This type of virus can affect both animals and humans. The virus is passed on to humans from animals through an infected mosquito.

Risk factors includes:

The region you visit
The time of year you visit
The activities you do


Blood tests: To know the antibodies present in the blood.

Lumbar puncture: It is also done to check for antibodies in CSF and spinal fluid.

Scans: In case of brain encephalitis:

A computerized tomography (CT) scan, which takes a series of X-rays of body at slightly different angles to produce a clear image of the inside of body
A magnetic resonance imaging (MRI) scan, which uses a strong magnetic field and radio waves to produce detailed images of the inside of body


There is no specific treatment for Japanese encephalitis, supportive treatment is provided. Measures can be taken to control symptoms and prevent complications from developing.


Prevention and control measures for Japanese Encephalitis (JE):
(A) At Individual Level
• Adopt measures to reduce vector density.
• Take personal protection measures against mosquito bites.
• Wear proper clothing to reduce mosquito bites specially during peak biting hours.
• Use of mosquito repellent creams, liquids, coils, mats etc.
• Use insecticide treated mosquito bed nets.
• Sleeping in rooms with close-fitting windows and doors.
• Spraying the room with insecticide specially in the early evening.
• Screening of the houses with wire mesh.
• DEET (diethyltoluamide) is most effective repellents and it is available in sprays, roll-ons, sticks and creams.
• Japanese encephalitis (JE) vaccination is an important tool for prevention. Three doses are given to an individual & vaccine can prevent Japanese encephalitis (JE) for a number of years.

(B) In the Community
• Malathion fogging during outbreaks.
• Sensitizing and involving the community for detection of vector.
• Adopt Eco-management system to reduce mosquito breeding.
• From human dwellings piggeries should be kept away,at least 4-5 kms.
• The place around the Hand Pump should be properly cemented and along with drainage system.

(C) Prevention During Travel
• If travelling, try to find out the Japanese encephalitis (JE) risk in that particular area and take the advice from doctor before visiting that area.

(D) Prevention of Japanese Encephalitis (JE) during Pregnancy
• Use of treated nets/LLINs(Long Lasting Insecticidal Nets).
• All the personal preventions as mentioned above.

Some Do's and Don't
• Don't spray/cream insect repellent directly onto your face, spray it onto your hands and then apply it to your face.
• Do not use it on cuts and wounds.
• Avoid area around eyes, lips, mouth and ears canal.
• Help children and youngsters to apply repellent. Don't allow young children to apply it themselves.
• Apply insect repellent after applying sunscreen.
• Wash your hands thoroughly after use.
• Wash the repellent off your skin with soap.
• Always follow the instructions written on the repellent.


It can lead to mild complications like:

Uncontrollable shaking of the hands
Changes to personality
Muscle weakness and twitching in the arms and hands.

Moderate disability can take the form of:
Mild learning difficulties
Paralysis of a single limb
Weakness on one side of the body

Centre of Disease Control and Prevention