Japanese encephalitis: symptoms, causes and epidemiology

Japanese encephalitis is one of the most common infectious diseases of the viral type in Asia. Although outbreaks are usually controlled by mass vaccination and symptoms are usually not severe, in some cases this virus is associated with dangerous inflammation of the brain that can leave significant damage or even cause death.

In this article we will describe what is Japanese encephalitis, what are its causes and what are its symptoms and the main signs. We will also explain in which places this disease occurs frequently and what measures can be taken to avoid contracting it, as well as the treatments usually recommended if it develops.

    What is Japanese encephalitis?

    Japanese encephalitis is an infectious disease that it is contracted by mosquito bites. It is caused by a virus endemic in 24 countries in East, South and Southeast Asia, as well as in the islands of the Western Pacific.

    In places like China, Thailand, Korea, Vietnam, India, Indonesia, Philippines, Taiwan, Myanmar, Sri Lanka, Cambodia, Laos, Nepal or Malaysia, the cases Japanese encephalitis are very common, although vaccines exist to prevent them. curiously, in Japan, this disease is rare for the effectiveness of vaccination programs.

    The virus that causes Japanese encephalitis is classified in the flavivirus familyTo which also belong that of yellow fever, dengue, West Nile virus and those that cause certain types of hepatitis.

    Although in a large number of cases the virus does not cause severe symptoms, more than a third of people with Japanese encephalitis suffer from permanent sequelae and about 30% die due to the changes resulting from brain inflammation.

      Signs and symptoms

      In most cases, contracting the Japanese encephalitis virus does not cause any symptoms, or only headaches and fever occur. however, sometimes inflammation of the brain develops (encephalitis) which can become serious.

      In one in 100 or 250 cases, the infection progresses to a disease that appears 5 to 15 days after the mosquito bite and can be life-threatening. The symptoms and signs characteristic of this phase are as follows:

      • Headache
      • intense fever
      • vomiting
      • disorientation
      • tremors
      • convulsions
      • Torticollis
      • spastic paralysis
      • cerebral coma

      Slightly less than a third of people infected with Japanese encephalitis are permanently affected by this virus. It is common for them to occur sequelae related to neurological disorders, Such as partial paralysis, loss of speech, and cognitive and behavioral disorders.

      Causes and epidemiology

      Japanese encephalitis is mainly transmitted by the Culex tritaeniorhynchus and Culex vishnui mosquito species. com animals farm pigs and herons are frequent carriers of the virus; mosquitoes infect humans and other animals, especially horses, through their bites.

      The disease mainly affects people in rural areas and surrounding areas of cities due to the closer proximity to animals; it is also associated with rice cultivation and flood irrigation. In comparison, it is relatively rare in urban areas.

      In Asia, they are recorded approximately 70,000 cases of Japanese encephalitis each year; the disease kills 13,000 to 20,000 people each year. However, most people in countries where Japanese encephalitis is endemic become immune after being vaccinated or contracted in childhood.

      Large Japanese encephalitis epidemics tend to occur in summer, although in countries with tropical climates the prevalence is high throughout the year and increases even more during the rainy season; this is linked to the increase in the number of mosquitoes. The frequency of intense outbreaks ranges from 2 to 15 years.

        Prevention and treatment

        There is no chaplain for Japanese encephalitis, so treatment is aimed at reducing symptoms, As well as the promotion of biological processes that allow elimination of infection. For these purposes, rest, large amounts of fluids and antipyretic and analgesic drugs are prescribed.

        In general, in countries in Asia and the Pacific where this virus is prevalent, there are medical protocols aimed at minimizing the risk of contracting the disease and experiencing the most severe effects, mainly through vaccination and surveillance of new cases and epidemics.

        Since people in other parts of the world are less prepared to defend themselves against Japanese encephalitis, it is advisable to get vaccinated preventively before going to places where you could contract the virus. Also using repellents and covering your arms and legs can prevent mosquito bites.

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