Japanese encephalitis
Japanese encephalitis (JE) is a viral infection transmitted through the bite of infected mosquitoes, leading to inflammation of the brain and central nervous system. It is primarily found in rural regions of Asia, with significant outbreaks reported in countries such as China, Korea, Japan, Taiwan, and Thailand. In addition, 24 countries in Southeast Asia and the Pacific experience endemic transmission. Risk factors for contracting JE include living or traveling in these areas, especially near rice paddies and farms where mosquitoes breed, and being very young, elderly, or immunocompromised. Symptoms typically arise 5 to 15 days after infection and can range from mild flu-like signs to severe complications, including confusion, convulsions, and coma. Diagnosing JE involves a medical history review, physical examinations, and various imaging and laboratory tests. While there is no specific treatment for Japanese encephalitis, supportive care is provided to manage symptoms. Vaccination is recommended for those in high-risk areas and for certain laboratory workers, alongside preventive measures such as using insect repellent and wearing protective clothing.
Japanese encephalitis
- ANATOMY OR SYSTEM AFFECTED: Brain, central nervous system
Definition
Japanese encephalitis is a mosquito-borne virus that leads to swelling of the brain. It can affect the central nervous system and cause severe complications, even death.
Causes
Japanese encephalitis is caused by the bite of a mosquito infected with the virus.
Risk Factors
The factors that increase the chance of being exposed to Japanese encephalitis include living or traveling in certain rural parts of Asia. According to the Centers for Disease Control and Prevention (CDC), outbreaks of Japanese encephalitis have occurred in China, Korea, Japan, Taiwan, and Thailand. These countries have controlled the disease through vaccinations. Other countries, including Vietnam, Cambodia, Myanmar, India, Nepal, and Malaysia, continue to have periodic epidemics. According to the World Health Organization (WHO) and the CDC, twenty-four countries in Southeast Asia and the Pacific region have endemic transmission of Japanese encephalitis. In the 2020s, Australia, Nepal, and India have all reported outbreaks. Also, laboratory workers who might be exposed to the virus are at high risk for developing Japanese encephalitis. Other risk factors include spending time outdoors at dawn and dusk, spending time at farms and in ride paddies that act as breeding grounds for mosquitoes, traveling to areas affected by irrigation or flooding, being very young or older, having a compromised immune system, and working in agriculture and animal husbandry.
Symptoms
Symptoms of Japanese encephalitis, which usually appear five to fifteen days after an infected mosquito bite, include agitation, brain damage, chills, coma, confusion, convulsions (especially in infants), fever, headache, nausea, neck stiffness, paralysis, tiredness, tremors, and vomiting. Additional symptoms include neurological issues, photophobia, phonophobia, loss of appetite, and muscle weakness. However, it is also important to note that most people will only experience mild, flu-like symptoms.
Screening and Diagnosis
A doctor will ask about symptoms and medical history and perform a physical exam. Tests may include blood tests to look for antibodies, a magnetic resonance imaging (MRI) scan (a scan that uses radio waves and a powerful magnet to produce detailed computer images), a computed tomography (CT) scan (a detailed X-ray picture that identifies abnormalities of fine tissue structure), and cerebrospinal fluid tests.
Treatment and Therapy
Because there is no specific treatment for Japanese encephalitis, care is concentrated on treating specific symptoms and complications.
Prevention and Outcomes
A Japanese encephalitis vaccine is recommended for people who live or travel in certain rural parts of Asia and for laboratory workers at risk of exposure to the virus. Also, to protect against mosquito bites and to prevent the disease, one should remain in well-screened areas, wear clothes that cover most of the body, and use insect repellents on skin and clothing that contain up to 30 percent N,N-diethyl-meta-toluamide (DEET).
Bibliography
Booss, John, Margaret Esiri, and Margaret M. Esin, editors. Viral Encephalitis in Humans. Washington, D.C.: ASM Press, 2003.
"Factsheet about Japanese Encephalitis." ECDC, 15 Dec. 2023, www.ecdc.europa.eu/en/japanese-encephalitis/facts. Accessed 1 Oct. 2024.
Goddard, Jerome. Physician’s Guide to Arthropods of Medical Importance. 4th ed., Boca Raton, Fla.: CRC Press, 2003.
Marquardt, William C., editor. Biology of Disease Vectors. 2d ed., New York: Academic Press/Elsevier, 2005.
Peters, C. J. "Infections Caused by Arthropod- and Rodent-Borne Viruses." Harrison’s Principles of Internal Medicine, edited by Anthony Fauci, et al. 17th ed., New York: McGraw-Hill, 2008.
"Treatment and Prevention of Japanese Encephalitis." CDC, 15 May 2024, www.cdc.gov/japanese-encephalitis/hcp/treatment-prevention/index.html. Accessed 1 Oct. 2024.