Japanese Encephalitis

Key points about Japanese encephalitis

• Japanese encephalitis is a viral encephalitis transmitted by mosquitoes, in tropical Asian and western Pacific areas.
• The majority of infections are asymptomatic, but the clinical forms are often severe, even fatal.
• La mortality and the risk of neurological sequelae are elevated in cases of encephalitis.
• There is no specific curative treatment.
• La vaccination and mosquito protection are the most effective means of prevention.

What is Japanese encephalitis?

Japanese encephalitis is a viral infectious disease due to Japanese encephalitis virus (JEV), a flavivirus. It is transmitted to humans by the bites from infected mosquitoesmainly of the kind Culex, after a zoonotic cycle involving mainly the pigs and birdsMan is a accidental host and plays no role in the transmission of the virus. The majority of infections are asymptomatic, but a small proportion progress to severe central nervous system involvement.

Japanese encephalitis worldwide

Japanese encephalitis is endemic to Asia and the western Pacific, particularly in South, Southeast and East Asia. It constitutes the leading cause of viral encephalitis in these regionswith tens of thousands of clinical cases each year. The risk is higher in rural or peri-urban areas, particularly in rice-growing and pig-raising regions. Children have historically been the most affected in endemic areas, but the non-immune adultsIn particular, travellers can also develop severe forms of the disease.

Symptoms of Japanese encephalitis

After an incubation period of 5 to 15 days, the infection is most often asymptomatic or paucisymptomatic. In less than 1% of cases, the disease progresses to a acute encephalitis, combining high fever, headaches, altered consciousness, seizures, and focal neurological deficits. Symptomatic forms are burdened with a high mortality (1/3 of cases) and frequent neurological sequelae (cognitive, motor or behavioral disorders, in 1/3 of cases also), particularly in children.

The diagnosis of Japanese encephalitis

The diagnosis of Japanese encephalitis is based on the epidemiological context (stay in an endemic area, exposure to mosquitoes) and the neurological clinical presentation. Confirmation is serological, by detecting virus-specific IgM antibodies in serum and/or cerebrospinal fluid. CSF analysis typically shows a lymphocytic meningoencephalitisBrain imaging can reveal damage to the basal ganglia or brainstem.

Treatment of Japanese encephalitis

There is no specific antiviral treatment against the Japanese encephalitis virus. Treatment is strictly symptomaticTreatment relies on hospitalization, management of neurological complications, and resuscitation if necessary. Preventing long-term effects depends on early and appropriate care.

Prevention

Prevention relies primarily on the vaccinationwhich is effective and recommended for people living in endemic areas and for certain exposed travelers (prolonged stays, rural areas, transmission season). The mosquito protection measures Essential items include: repellents, mosquito nets, protective clothing, air conditioning, and insecticides. There are no no human-to-human transmission.