Japanese encephalitis

The virus responsible for Japanese Encephalitis Virus (JEV) is a single-stranded RNA Flavivirus related to those that cause serious diseases such as yellow fever, transmitted from animals to humans. It typically has animals such as pigs and birds as breeding reservoirs, while it is transmitted by mosquitoes.

JEV virus is transmitted to humans through the bite of infected Culexmosquitoes, particularly Culex tritaeniorhynchus. The virus is maintained in a cycle between mosquitoes and vertebrate hosts, mainly pigs and wading birds. Humans are secondary hosts or dead ends because they usually do not develop high enough concentrations of JE virus in their bloodstreams to infect mosquitoes and thus continue transmission. JEV primarily affects children. Most adults in endemic countries have natural immunity after childhood infection, but still individuals of any age can be affected.

The risk of Japanese encephalitis exists in 24 countries in Southeast Asia and the East Pacific, in an area and affecting more than 3 billion people, where it causes large outbreaks, with greatest intensity during the rainy season. It is typically concentrated in agricultural or rural areas, where mosquitoes find suitable habitat among rice paddies and farms, but cases are increasing in urban areas.

Japanese encephalitis is in most cases asymptomatic. Only less than 1% of infected individuals manifest obvious symptoms such as headache, fever, fatigue, malaise, nausea, and vomiting after an incubation period of 5 to 15 days.
It can worsen with neurological symptoms such as neck stiffness, headache, seizures, altered consciousness, and spastic paralysis (1 in 250 cases). The most severe forms evolve into an acute viral encephalitis, with a lethality rate of 30%, characterized by a parkinsonian syndrome. Up to 30% of those who survive may manifest neurological or psychiatric deficits.

The diagnosis of Japanese encephalitis is based on anamnestic assessment (identifying recent travel to endemic area, for example) and clinical evaluation.
Individuals who live in or have traveled to an endemic area and experience encephalitis are considered a suspected case of JE. Laboratory testing is required to confirm JEV infection and exclude other causes of encephalitis. WHO recommends testing for JEV-specific IgM antibody in a single cerebrospinal fluid or serum sample using an ELISA test.

To date, there is no specific treatment for JEV infections. Treatment is based on treating symptoms and supporting vital functions, often with hospitalization.

Prevention for Japanese encephalitis transmission begins with proper behavioral prophylaxis, especially during the day, a time when mosquitoes are most active.
- Use an effective mosquito repellent.
The Centers for Disease Control and Prevention (CDC) recommends repellents with the following active ingredients: DEET (>25%); Picaridin; IR3535; Eucalyptus Lemon Oil (OLE); Para-menthane-diol; 2- undecanone.
- Cover up.
Use clothing that covers your legs and arms, preferably light colored.
- Check the environment around you
Standing water is a perfect habitat for mosquitoes to breed. Make sure there is no stagnant water in: discarded tires or industrial containers, swimming pools, storm drains and saucers. To reduce the risk ti transmission, systematic control through pest control campaigns against the Aedes population turns out to be a key intervention.There is also a vaccine, which is extremely effective in avoiding the disease, that is administered intramuscularly with two doses 28 days apart.