What happens when you get Japanese encephalitis?

About 30% of Japanese encephalitis cases are fatal and half of survivors must permanently live with sequelae ranging from paralysis to intellectual disability.

Japanese encephalitis is caused by Japanese encephalitis virus (JEV) group B. The disease was first discovered in Japan and Japanese scientists isolated the virus in 1935, so the disease was named Japanese encephalitis.

JEV is transmitted by Culex mosquitoes, which, after sucking blood from infected animals, are then transmitted to humans through mosquito bites. Animals that carry Japanese encephalitis are usually livestock such as pigs, cattle, horses, etc. and wild birds.

After entering the body, the Japanese encephalitis virus attacks the central nervous system and invades the brain, causing swelling, inflammation and often damage to the most important and complex organs. The patient may suffer severe physical disabilities or mental changes. Sometimes, the most obvious symptom of JE is behavioral changes, leading to an incorrect psychiatric diagnosis.

Only one in 250 cases of Japanese encephalitis results in serious symptoms, but the mortality rate is high, between 30 and 50%. For most survivors, the after-effects of the disease are severe.

According to an article published in the British Medical Journal , 30% of people with JE live with motor impairment due to deformities of the arms and legs, 20% have severe cognitive and language impairment, and another 20% have seizures. Approximately 30-50% of cases will live with permanent psychiatric sequelae. A study in Gansu, China, found neurological sequelae in 44.7% of JE patients, including subnormal intelligence, as assessed by IQ, in 21.2% of subjects.

In addition, the disabilities after JE are very diverse, such as: loss of vision; physical disabilities leading to complete dependence on family care; dependence on ventilators and inability to stand up or struggling with persistent fatigue after several years of illness. Often, even those who are considered to "recover well" after JE experience changes such as: difficulty in learning, behavioral or neurological changes that are difficult to detect.

According to the World Health Organization (WHO), an estimated 68,000 people worldwide contract Japanese encephalitis each year. Of these, 75% occur in children aged 14 and under, and about 15,000-20,000 die. These numbers are likely to increase due to population growth, climate change, and land use patterns that make large areas of the world more conducive to the spread of the Japanese encephalitis virus.

JEV is the leading cause of encephalitis in Asia, including Vietnam. The disease can occur year-round but peaks from May to August. It can occur at any age but is most common in children aged 2 to 8 years old.

Vaccination against Japanese encephalitis is still the best way to reduce the risk of infection and mortality. Photo: Freepik

There is currently no specific antiviral treatment for Japanese encephalitis and treatment is aimed at relieving symptoms. Mosquito nets and insect repellents can help reduce the risk of infection, but vaccination remains the most effective way to prevent the disease, reduce the severity of symptoms of JE and reduce mortality.

According to WHO, there are currently four types of Japanese encephalitis vaccines in use, including inactivated vaccines derived from mouse brain, inactivated vaccines derived from vero cells, live attenuated vaccines, and live recombinant vaccines.

The Department of Prevention, Ministry of Health , said that before the Japanese encephalitis vaccine Jevax was deployed in the National Expanded Immunization Program, JEV was the cause of about 25-30% of encephalitis cases hospitalized, many of which were fatal. Currently, this rate has decreased (to less than 10%) after many years of implementing vaccination for children of the age, with vaccination rates maintained at a high level.

Currently, Vietnam has two types of Japanese encephalitis vaccines for children and adults: Imojev and Jevax. For Jevax, if only one injection is given, it will not be effective. Children who have received three injections will have a 90-95% protection rate for about three years. A booster shot is needed every three to four years until the child turns 15. With the Imojev vaccine, children from 9 months to 18 years old only need one basic dose and one booster shot after one year to create enough immunity. People aged 18 years and older only need one injection.

Many cases of Japanese encephalitis are due to non-compliance with the vaccination schedule. Therefore, to ensure the best immune effect, everyone needs to get enough doses, on schedule as recommended.

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