Japanese encephalitis is a potentially severe viral disease that is spread by infected mosquitoes in the agricultural regions of
Japanese encephalitis is a disease that is spread to humans by infected mosquitoes in
Japanese encephalitis is caused by the Japanese encephalitis virus, an arbovirus, which is an arthropod-borne virus. Arboviruses are a large group of viruses that are spread by certain arthropods, most commonly blood-sucking insects. Japanese encephalitis is spread by infected mosquitoes.
Japanese encephalitis is found throughout rural areas in
Mode of infection
Japanese encephalitis virus has a complex life cycle involving domestic pigs, birds and a specific type of mosquito, Culex tritaeniorhynchus that lives in rural rice-growing and pig-farming regions. The mosquito breeds in flooded rice fields, marshes, and standing water around planted fields. The virus can infect humans, most domestic animals, birds, bats, snakes, and frogs. After infection, the virus invades the central nervous system, including the brain and spinal cord. Mosquitoes become infected by sucking blood from domestic pigs and wild birds infected with the Japanese encephalitis virus. Infected mosquitoes then transmit the virus to humans and animals during the feeding process. The virus multiplies in the blood systems of domestic pigs and wild birds. Among persons who are infected by a mosquito bite, only 1 in 50 will develop an illness. Japanese encephalitis is the leading cause of viral encephalitis in
Most infected persons develop mild symptoms or no symptoms at all. In people who develop a more severe disease, it starts as a flu-like illness, with fever, chills, tiredness, headache, nausea, and vomiting. Confusion and agitation can also occur in the early stage. The illness can progress to a serious infection of the brain (encephalitis) and can be fatal in 30% of cases. Among the survivors, another 30% will have serious brain damage, including paralysis. Mild infections may occur without apparent symptoms other than fever with headache but in the case of more severe infections there is headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions and spastic paralysis.
Symptoms usually appear 6-8 days after the bite of an infected mosquito, incubation period being 5-15 days.
Diagnosis is based on tests of blood or spinal fluid.
There is no specific treatment for Japanese encephalitis. Antibiotics are not effective against viruses, and no effective anti-viral drugs have been developed. Care of patients centres on treatment of symptoms and complications.
Vaccination is recommended only for persons who plan to travel in the infection prone areas for 4 weeks or more and in special circumstances such as an ongoing outbreak of disease.
Because of the potential for other mosquito-borne diseases in