Japanese encephalitis: symptoms, causes and epidemiology
May 10, 2023
One of the most common viral infectious diseases in Asia is Japanese encephalitis. Although outbreaks are usually controlled by mass vaccination and symptoms are usually not severe, in some cases this virus is associated with a dangerous inflammation of the brain that can leave significant sequelae or even cause death.
In this article we will describe what is japanese encephalitis, what causes it and what are its symptoms and main signs. We will also explain in which places this disease appears frequently and what measures can be take to prevent contracting it, as well as the care that is usually recommended in case it occurs. I developed.
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What is Japanese encephalitis?
Japanese encephalitis is an infectious disease that contracted through mosquito bites. It is caused by a virus endemic to 24 countries in East, South, and Southeast Asia, as well as the islands of the Western Pacific.
In places like China, Thailand, Korea, Vietnam, India, Indonesia, the Philippines, Taiwan, Myanmar, Sri Lanka, Cambodia, Laos, Nepal or Malaysia, cases of Japanese encephalitis are very common, although there are vaccines to prevent them; Curiously, in Japan this disease is rare due to the effectiveness of immunization programs.
The virus that causes Japanese encephalitis It is classified in the flavivirus family., to which yellow fever, dengue, West Nile virus and those that cause some types of hepatitis also belong.
Although in a large part of the cases the virus does not cause the appearance of severe symptoms, more than a third of people with Japanese encephalitis suffer permanent sequelae and approximately 30% die from alterations derived from inflammation cerebral.
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Signs and symptoms
In most cases contracting the Japanese encephalitis virus does not cause any symptoms, or only a headache and fever occur. However, sometimes an inflammation of the brain (encephalitis) develops which can become serious.
In one out of every 100 or 250 cases, the infection progresses to give way to a disease that appears between 5 and 15 days after the mosquito bite and can endanger the person's life. The characteristic symptoms and signs of this phase are the following::
- high fever
- stiff neck
- spastic paralysis
- brain coma
Slightly less than a third of people infected with Japanese encephalitis are permanently affected by this virus. It is common for them to sequelae related to neurological alterationssuch as partial paralysis, loss of speech, and cognitive and behavioral disorders.
Causes and epidemiology
Japanese encephalitis is transmitted primarily by the Culex tritaeniorhynchus and Culex vishnui species of mosquitoes. animals like farmed pigs and herons frequently carry the virus; mosquitoes infect people and other animals, especially horses, through their bites.
The disease mainly affects populations in rural areas and in the regions surrounding cities due to the greater proximity of animals; it is also associated with rice cultivation and flood irrigation. By comparison, it is relatively rare in urban areas.
In Asia there are approximately 70 thousand cases of Japanese encephalitis each year; The disease causes the death of between 13,000 and 20,000 people annually. However, most people in countries where Japanese encephalitis is endemic become immune after being vaccinated or contracted during childhood.
Large epidemics of Japanese encephalitis tend to occur in summer, although in countries of tropical climate the prevalence is high throughout the year and increases even more in the season rainy; this is related to the increase in the number of mosquitoes. The frequency of occurrence of intense outbreaks ranges from approximately 2 to 15 years.
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Prevention and treatment
There is no cure for Japanese encephalitis, so treatment is aimed at reducing symptoms, as well as favoring the biological processes that allow the elimination of the infection. For these purposes, rest, large amounts of fluids, and antipyretic and analgesic medications are prescribed.
In general, in the countries of Asia and the Pacific where this virus is common, there are medical protocols aimed at minimizing the risk of contracting the disease and suffering its most serious effects, mainly through vaccination and surveillance of the appearance of new cases and epidemics.
Since people in other regions of the world are not as prepared to defend themselves against encephalitis In Japan, it is advisable to get vaccinated preventively before traveling to places where you could contract the virus. virus. Also using repellent products and covering arms and legs can prevent mosquito bites.