Each year, it is estimated that between 13,600 and 20,400 cases of the Japanese Encephalitis virus infecting a human being take place. Furthermore, it is believed that, of those who survive, between 14,300 and 27,200 go on to develop long term neurological problems.
Japanese Encephalitis (JE) is classified as a flavivirus – a type of virus which is related to yellow fever, dengue fever and West Nile virus. These viruses are spread to the human population by mosquitoes. In the case of JE, it is usually found in South Asia, South-East Asia, East Asia and the Pacific. This part of the world is where almost one half of the entire human population lives, and is continually at risk from endemic viruses such as JE.
Children are considered to be the group most at risk, and survivors go on to develop immunity to the virus during adulthood. However, those who have never been exposed to the virus continue to be at risk into middle age and later life. Those who live in rural areas are at a higher risk than city dwellers.
The main culprit for the spread of JE to humans is the Culex tritaeniorhynchus mosquito, along with a number of related species. These insects typically lay their eggs in rice paddies and bodies of standing water. They usually acquire the virus after feeding on the blood of pigs and birds. If a mosquito bites an infected human and then goes on to bite other humans, the virus will not be transmitted, however, as it cannot reproduce to a high enough viral load in order to ensure it spreads further.
It is very possible to be infected with JE and not know about it. Many of the infected show no symptoms at all, while others might display flu-like symptoms. However, around one person in 250 will suffer from a high fever, seizures, a stiff neck, confusion, the inability to speak, general weakness or even paralysis. Furthermore, around a third of those infected will die. The incubation period lasts typically between five and fifteen days. For survivors of JE, there are still often problems to contend with. Around one third may develop an inflammation of the brain.
While anyone can be infected, there are obviously some groups which are at a higher risk. These include those who live or work near pig farms or paddy fields, and visitors (including travelers) to those areas. Those who sleep exposed in endemic areas are particularly at risk.
There is no cure for JE, and treatment rests on alleviating any symptoms. There is, however, a vaccine, which should be taken by anyone planning to spend time in areas where JE is found. Some countries have prioritized this type of immunization, especially for children, although it is important to consult your doctor to see whether it is suitable for you or not. Furthermore, it is important to minimize the risk of being bitten by an infected mosquito. This can be done by wearing long sleeves, applying mosquito repellent and using mosquito nets and mesh.