Japanese Encephalitis( JE)
It is caused by a virus called JE Virus or JEV. It is now endemic in Asia. Most cases occur in the beginning of rainy season.
The disease is spread by mosquitoes. The virus multiplies in pigs and aquatic birds. When a mosquito bites human beings after biting pigs the virus is transmitted to man. Pigs are the most important hosts due to very high levels of virus in their blood.
In man the virus multiplies but does not reach levels where a mosquito after biting one human being can transmit it to others. The name of mosquito spreading it most often is Culex Vishnui. However, it is found in other species of mosquitoes as well.
After a gap of 5 to 15 days (called incubation period), signs and symptoms of the disease appear.
Most of the cases where the bite transmits the virus are subclinical or mild. Only about 1% of the cases are severe and brain inflammation or encephalitis is seen.
In the beginning, there is fever and sometimes loose motions and body aches. Chills and rigors, headache and vomiting may occur. A few days later involvement of the brain is seen with the occurrence of fits, drowsiness, and patients may become unconscious.
Diagnosis is achieved by finding antibodies against this virus in the blood (ELISA Test) and rarely by finding viral particles (NAAT )
They may remain bedridden for weeks.
20 to 30 % of the patients who are hospitalised with JE die due to the illness. Of the survivors, 40 to 50 % may have permanent neurological damage.
Prevention is accomplished by preventing mosquito bites.
A vaccine grown in vera cell line given in doses of .5 ml on day 0 and 28 is available for adults. A live attenuated vaccine and other vaccines have also been manufactured. These vaccines may have side effects.
The efficacy of the vaccine is not yet clear.