Japanese Encephalitis (JE)

                    Japanese Encephalitis (JE) is a type of viral brain infection that's spread through mosquito bites. Symptoms usually take 5-15 days to develop and include fever, headache, vomiting, confusion, and difficulty moving. Symptoms that develop later include swelling around the brain and coma. JE is a serious disease that may cause death. Although symptomatic Japanese encephalitis (JE) is rare, the case-fatality rate among those with encephalitis can be as high as 30%. Permanent neurologic or psychiatric sequelae can occur in 30%–50% of those with encephalitis.

Causes
Japanese encephalitis is caused by a flavivirus, which can affect both humans and animals. The virus is passed from animals to humans through the bite of an infected mosquito. Pigs and wading birds are the main carriers of the Japanese encephalitis virus.

Symptoms
1. Less than 1% of people infected with Japanese encephalitis (JE) virus develop clinical illness.
2. In persons who develop symptoms, the incubation period (time from infection until illness) is typically 5-15 days.
3. Initial symptoms often include fever, headache, and vomiting.
4. Mental status changes, neurologic symptoms, weakness, and movement disorders might develop over the next few days.
5. Seizures are common, especially among children.

Diagnosis
- To confirm JEV infection and to rule out other causes of encephalitis requires a laboratory testing of serum or, preferentially, cerebrospinal fluid.
- Surveillance of the disease is mostly syndromic for acute encephalitis. Confirmatory laboratory testing is often conducted in dedicated sentinel sites, and efforts are undertaken to expand laboratory-based surveillance. Case-based surveillance is established in countries that effectively control JE through vaccination.

Treatment
A. No specific treatments have been found to benefit patients with JE, but hospitalization for supportive care and close observation is generally required.
B. Treatment is symptomatic. Rest, fluids, and use of pain relievers and medication to reduce fever may relieve some symptoms.

Prevention and Control
Safe and effective JE vaccines are available to prevent disease. WHO recommends having strong JE prevention and control activities, including JE immunization in all regions where the disease is a recognized public health priority, along with strengthening surveillance and reporting mechanisms. Even if the number of JE-confirmed cases is low, vaccination should be considered where there is a suitable environment for JE virus transmission. There is little evidence to support a reduction in JE disease burden from interventions other than the vaccination of humans.

There are 4 main types of JE vaccines currently in use: inactivated mouse brain-derived vaccines, inactivated Vero cell-derived vaccines, live attenuated vaccines, and live recombinant vaccines.

Over the past years, the live attenuated SA14-14-2 vaccine manufactured in China has become the most widely used vaccine in endemic countries, and it was prequalified by WHO in October 2013. Cell-culture based inactivated vaccines and the live recombinant vaccine based on the yellow fever vaccine strain have also been licensed and WHO-prequalified. In November 2013, Gavi opened a funding window to support JE vaccination campaigns in eligible countries.

All travellers to Japanese encephalitis-endemic areas should take precautions to avoid mosquito bites to reduce the risk for JE. Personal preventive measures
include the use of repellents, long-sleeved clothes, coils and vaporizers. Travellers spending extensive time in JE endemic areas are recommended to get vaccinated.

Reference :

1. WHO : Japanese encephalitis, 2015.

2. CDC : Japanese Encephalitis, August 5, 2015.