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Japanese Encephalitis - Causes, Symptoms, Diagnosis, Treatment and Prevention

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Japanese encephalitis (JE) is one of the most commonly occurring viral infections via mosquitoes. Read the article to know more about it.

Medically reviewed by

Dr. C. Elanchezhian

Published At April 16, 2022
Reviewed AtMay 24, 2024

What Is Meant by Japanese Encephalitis?

Japanese encephalitis, a virus from the flavivirus family, is transmitted by the Culex mosquito. The virus can infect not only humans but also horses and pigs. In horses, it can cause encephalitis, while in pigs, it may result in miscarriage. In the transmission of a virus, the host is the source, while the vector is responsible for its transmission. Wild birds are likely the natural hosts of Japanese encephalitis virus (JEV), and mosquitoes serve as the vectors. While the vector does not cause the disease, it facilitates its transmission. When mosquitoes infect an animal, the animal may become a carrier of the virus. Subsequently, when other mosquitoes feed on these newly infected animals, they acquire the virus and can then transmit it to other animals. People face the highest risk of Japanese encephalitis in rural areas where the virus is prevalent. The virus is commonly found in and around towns and cities. Children are more susceptible to Japanese encephalitis because adults living in areas where the virus is endemic typically develop immunity as they age.

What Are the Common Geographical Locations Affected by Japanese Encephalitis?

Japanese encephalitis is most commonly found throughout Southeast Asia. While China, Korea, Japan, Taiwan, and Thailand have experienced outbreaks in the past, they have largely controlled the disease through vaccination. However, Vietnam, Cambodia, Myanmar, India, Nepal, and Malaysia still experience occasional epidemics. Although there have been cases reported in northern Australia, health authorities in mainland Australia consider the disease to be low-risk. In the United States, there have been a few reports of Japanese encephalitis in individuals who have traveled to regions where the disease is active. Overall, the likelihood of contracting Japanese encephalitis while traveling in Asia is extremely low. However, this risk can vary depending on factors such as the season, travel destination, duration of stay, and the activities undertaken by travelers in Asia. The risk of Japanese encephalitis is highest during the transmission season, but this varies depending on the region:

  • In temperate regions, transmission peaks during the summer and early fall, typically between May and September.

  • In subtropical and tropical areas, the transmission season is influenced by rainfall patterns and bird migrations.

  • In certain tropical regions, transmission can occur throughout the year, influenced in part by agricultural practices.

  • The disease is more prevalent in regions where rice cultivation is common.

What Are the Symptoms of Japanese Encephalitis?

People affected by Japanese encephalitis do not show symptoms, but in case they develop symptoms, it happens within 5 to 15 days after they get infected. It can be mild or severe. The mild symptoms usually include fever with a headache, but severe cases develop serious symptoms very fast.

The following are the symptoms that can be witnessed:

  1. High fever.

  2. Tremors.

  3. Nausea.

  4. Vomiting.

  5. Headache.

  6. Stiffness in the neck.

  7. Spastic paralysis.

There may be changes in the brain functioning, and these may be as follows:

  1. Disorientation.

  2. Stupor.

  3. Coma.

  4. Children may develop convulsions.

The swelling of the testicles and the lower limb or leg is also seen.

When the individual develops brain symptoms, the effects can be lifelong and include hearing loss, difficulty in controlling emotions, and body weakness on one side. The survival rate varies among different age groups, but children are more prone to fatality.

How Can Japanese Encephalitis Be Diagnosed?

Initially, when the person visits the physician, they will be asked questions about their personal and medical history, followed by the symptoms they are facing. Then, questions will be asked about the stay and visited places. After that, certain physical examinations may be done, and they will be asked to do some laboratory and imaging tests, such as CT (computed tomography) and MRI (magnetic resonance imaging) of the brain.

A lumbar puncture may be done to obtain spinal fluid to check CSF (cerebrospinal fluid) for the exact type of virus causing the encephalitis. Human antibodies can be detected using immunofluorescence tests. Certain blood tests can also be performed.

What Are the Treatment Options Available for Japanese Encephalitis?

According to studies and research, no treatment or cure is available for JE. Only symptomatic treatment is possible. Antiviral drugs can be prescribed. The best way is to prevent the disease. Patients who survive the condition develop lifelong immunity.

How Can Japanese Encephalitis Be Prevented?

The main prevention mode is vaccination; insect repellent can also be used.

Vaccination:

The vaccination for JE is given over two doses. The duration between the first and second doses is 28 days. Another way of giving vaccination is in an accelerated schedule where there is only a seven-day difference between the two doses. However, the accelerated schedule is indicated in people between 18 to 65 years of age. Some symptoms may be seen post-injection of the JE vaccine, which may be as follows:

  1. Headache.

  2. Pain in the muscles.

  3. The site of injection can be red, sore, and swollen.

  4. Hives and difficulty in breathing can happen but in rare instances.

DEET(N,N-Diethyl-meta-toluamide) Insect Repellants:

People spending time outdoors in rural areas should take precautions such as wearing protective clothing and using bed nets. It is also advisable to sleep in air-conditioned or well-screened rooms. Individuals new to an area where Japanese encephalitis is prevalent typically do not have a natural immunity to the virus. Therefore, travelers of all ages are more susceptible to infection compared to those who have always lived in areas where the disease is common. During an outbreak, communities affected by Japanese encephalitis should eliminate pools of standing water where mosquitoes breed and use insect repellent. Loose-fitting clothing can also help prevent mosquito bites. The most effective insect repellents contain a chemical called DEET.

Conclusion:

Japanese encephalitis is a viral infection that may affect the brain and certain other parts of the body and, ultimately, affect the quality of life. Certain complications can be there for a long time, and hence, it is advisable to consult the physician as soon as possible when the person experiences some symptoms or is planning to visit or return from an affected geographic location. With the help of online platforms, it has become very easy to consult a physician or specialist at the ease of home. Hence, consult a physician to get more details about the same.

Frequently Asked Questions

1.

Is It Necessary to Get the Japanese Encephalitis Vaccine?

The Japanese encephalitis Vaccine is required for those traveling to areas endemic to the viral infection(southeast Asian countries). Otherwise, it is not mandatory to get the vaccine. Japanese encephalitis is a viral infection that spreads through mosquitoes.

2.

Which Organ Is Affected by Japanese Encephalitis?

The symptoms of Japanese encephalitis are high fever, nausea, and headache. Few infections can spread and affect the brain. Many people recover completely from the brain damage, but few have permanent brain damage, such as seizures, memory loss, and irritability, and may require long-term treatment.

3.

What Are the Measures to Protect Ourselves From Japanese Encephalitis?

It is important to prevent mosquito bites by wearing long-sleeved shirts and pants, using mosquito repellent, and getting vaccinated before traveling to protect ourselves from Japanese encephalitis. The Japanese encephalitis Vaccine is required for those traveling to areas endemic to the viral infection(southeast Asian countries).

4.

How Does Japanese Encephalitis Spread?

Japanese encephalitis is a viral infection that spreads through mosquitoes. But it does not spread from one person to another. Japanese encephalitis is spread through bites of mosquitoes of Culex species (culex tritaeniorhynchus).

5.

What Are the Contraindications of the Japanese Encephalitis Vaccine?

Babies below two months are not advised to get the Japanese encephalitis vaccine since its safety and effectiveness in this age group are unclear. The vaccine should be given in two doses. The first dose can be given to adults and children above two months. The second dose is given 28 days later. For adults aged 18 to 65, the second dose can be given as early as seven days after the first dose.

6.

When Should the Japanese Encephalitis Vaccine Be Given?

The vaccine should be given in two doses. The first dose can be given to adults and children above two months. The second dose is given 28 days later. For adults aged 18 to 65, the second dose can be given as early as seven days after the first dose. Both doses should be given at least seven days before travel.

7.

Can the Brain Recover From Japanese Encephalitis?

The symptoms of Japanese encephalitis are high fever, nausea, and headache. Few infections can spread and affect the brain. Many people recover completely from the brain damage, but few have permanent brain damage, such as seizures, memory loss, and irritability, and may require long-term treatment.

8.

Does Japanese Encephalitis Spread From One Human to Another?

No, Japanese encephalitis can not spread from person to person. It can only spread through mosquito bites. Japanese encephalitis is spread through bites of mosquitoes of Culex species (culex tritaeniorhynchus).

9.

What Age Group Is Eligible For the Japanese Encephalitis Vaccine?

The vaccine for Japanese encephalitis can be given to all adults and children above the age of 2 months. The vaccine should be given in two doses. The first dose can be given to adults and children above two months. The second dose is given 28 days later. For adults aged 18 to 65, the second dose can be given as early as seven days after the first dose. Both doses should be given at least seven days before travel.

10.

Does Japanese Encephalitis Spread Through All Types of Mosquitoes?

Japanese encephalitis is spread through bites of mosquitoes of Culex species (culex tritaeniorhynchus). Japanese encephalitis can not spread from person to person. It can only spread through mosquito bites.

11.

Should Japanese Encephalitis Be Worried About?

Japanese encephalitis causes no symptoms or mild symptoms like fever, nausea, headache, and neck stiffness. However, in a few cases, the infection spreads to the brain and may cause brain damage. Some people recover completely from the brain damage, but few have permanent brain damage, such as seizures, memory loss, and irritability.

12.

Does Japanese Encephalitis Cause Permanent Damage?

Most people affected with Japanese encephalitis show no symptoms or have mild symptoms and recover soon. But when the infection spreads to the brain, it can cause permanent brain damage, which can take years to recover.

13.

What Happens When Infected With Japanese Encephalitis?

Japanese encephalitis is a viral infection that spreads through mosquito bites. It can cause symptoms like high fever, nausea, vomiting, headache, neck stiffness, tremors, and paralysis. In some cases, the infection spreads to the brain and may cause brain damage, such as seizures, memory loss, and irritability.

14.

What Are the Benefits of the Japanese Encephalitis Vaccine?

The Japanese encephalitis vaccine can prevent you from getting infected by mosquito bites if you plan to travel and stay in areas endemic to Japanese encephalitis, like in Southeast Asian countries (China, Japan, Korea, and Thailand).
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Dr. C. Elanchezhian
Dr. C. Elanchezhian

General Medicine

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