Q. How is
Japanese encephalitis transmitted?
A. By rice field breeding mosquitoes (primarily the Culex
tritaeniorhynchus group) that become infected with Japanese
encephalitis virus (a flavivirus antigenically related to St.
Louis encephalitis virus).
How do people get Japanese encephalitis?
A. By the bite of mosquitoes infected with the Japanese
What is the basic transmission cycle?
A. Mosquitoes become infected by feeding on domestic pigs and
wild birds infected with the Japanese encephalitis virus. Infected
mosquitoes then transmit the Japanese encephalitis virus to humans
and animals during the feeding process. The Japanese encephalitis
virus is amplified in the blood systems of domestic pigs and wild
Could you get the Japanese encephalitis from another person?
A. No, Japanese encephalitis virus is NOT transmitted from
person-to-person. For example, you cannot get the virus from
touching or kissing a person who has the disease, or from a health
care worker who has treated someone with the disease.
Could you get Japanese encephalitis from animals other than domestic
pigs, or from insects other than mosquitoes?
A. No. Only domestic pigs and wild birds are carriers of the
Japanese encephalitis virus.
What are the symptoms of Japanese encephalitis?
A. Mild infections occur without apparent symptoms other than
fever with headache. More severe infection is marked by quick onset,
headache, high fever, neck stiffness, stupor, disorientation, coma,
tremors, occasional convulsions (especially in infants) and spastic
(but rarely flaccid) paralysis.
What is the incubation period for Japanese encephalitis?
A. Usually 5 to 15 days.
What is the mortality rate of Japanese encephalitis?
A. Case-fatality rates range from 0.3% to 60%.
How many cases of Japanese encephalitis occur in the world and the
A. Japanese encephalitis is the leading cause of viral
encephalitis in Asia with 30-50,000 cases reported annually. Fewer
than 1 case/year is reported in U.S. civilians and military
personnel traveling to and living in Asia. Rare outbreaks in U.S.
territories in Western Pacific have occurred.
How is Japanese encephalitis treated?
A. There is no specific therapy. Intensive supportive therapy is
Is the disease seasonal in its occurrence?
A. Seasonality of the illness varies by country
Q. Who is at risk for getting Japanese
A. Residents of rural areas in endemic locations, active duty
military deployed to endemic areas, and expatriates who visit rural
areas. Japanese encephalitis does not usually occur in urban areas.
Where is Japanese encephalitis endemic?
Where do Japanese encephalitis outbreaks occur?
Japanese encephalitis outbreaks are usually circumscribed and do not
cover large areas. They usually do not last more than a couple of
months, dying out after the majority of the pig amplifying hosts
have become infected. Birds are the natural hosts for Japanese
encephalitis. Epidemics occur when the virus is brought into the
peridomestic environment by mosquito bridge vectors where there are
pigs, which serve as amplification hosts, infecting more mosquitoes
which then may infect humans. Countries which have had major
epidemics in the past, but which have controlled the disease
primarily by vaccination, include China, Korea, Japan, Taiwan and
Thailand. Other countries that still have periodic epidemics include
Viet Nam, Cambodia, Myanmar, India, Nepal, and Malaysia.
Data from CDC
Q. Is there
any vaccine available against JE virus in India?
Mouse Brain-Derived JE Vaccine is available against JE in India. The
Vaccine is prepared by subjecting the mouse brain infected with
Nakayama strain of JE virus to a sequence of protamine sulphate
treatment, formalin inactivation and ultrafilteration and ammonium
sulfate precipitation. The purified product is without myclin basic
protean and supplied in a freeze dried form. The Vaccine in
manufactured at Central Research Institute, Kasauli, Himachal
Q. Who should be
vaccinated against Japanese Encephalitis?
studies disclose nearly universal infection by early adulthood and
in areas where viral transmission is particularly intense
Seroprevalance rates may increase during childhood. The age group
for immunization should be decided based on available Sero-epidemiological
data from the area.