Japanese Encephalitis (JEV) is an infection caused by a virus that affects the brain. JEV is related to yellow fever, dengue, and West Nile viruses. This virus is naturally found in some animals, such as pigs and birds, and is passed on to humans by mosquitos once they have consumed the blood of these animals. Japanese encephalitis cannot be passed from person to person.
Although Japanese encephalitis is rare, there are still an estimated 68,000 cases every year. Countries such as China, Vietnam, India, Indonesia, Malaysia, Thailand, and the Philippines have seen most of the cases of this virus. Mass immunisation means that despite the name Japanese encephalitis, there are now very few cases in Japan itself.
Many cases are not serious, but for those who do go on to develop severe illness, the death rate can be as high as 30%. Those who survive serious illness can sometimes be left permanently neurologically or psychiatrically damaged by this virus.
Symptoms of JEV include mild flu-like symptoms such as fever and headaches. However, approximately one in every 250 infections can lead to severe illness. It can take anything from four to 14 days for symptoms to appear. In children, these symptoms can include stomach pains and vomiting.
High fever, neck stiffness, paralysis, seizures, and eventual coma can be experienced by both children and adults in extreme cases. This ultimately can lead to death.
The transmission for JEV from animal to human is through mosquito bites. If a mosquito feeds on an infected animal and then bites a human, the live virus directly enters the bloodstream and then continues to multiply in the human body.
Risk factors for developing JEV are visiting or living in rural areas of the worst affected countries, especially during the rainy season when there are areas of stagnant water that have become breeding grounds for large numbers of mosquitos.
If an individual lives in or has recently visited an area with a high number of Japanese encephalitis cases, and neurological or even mild symptoms are also present, then this is enough to suspect a possible case of JEV. In this instance, a healthcare professional should order a lab test for JEV-specific IgM antibodies in serum or cerebrospinal fluid samples.
There currently are no antivirals that are effective against this virus. Medical treatment can only focus on lowering fever and pain management in mild cases. More severe cases can lead to death if patients are in intensive care.
There are effective vaccines that help to prevent infection with JEV, and making this vaccine available to those most at risk can help prevent outbreaks of this illness.
Not visiting areas with high incidences of this virus is also advisable, and for those who live in these regions, covering up bare skin, sleeping with the windows shut and mosquito net protection up, along with the use of insect repellents, can all prevent individuals from becoming infected with this virus.