A National Warning
In July, during one of Japan’s routine piggery screening, for antibodies to Japanese encephalitis virus, one pig out of 15 tested positive, indicating it had been recently exposed to the virus. A warning was consequently issued by the Japanese government to its citizens, informing them that the virus was present and active in their communities, and advising they take precautions to avoid mosquito bites. What’s more, further statements have been released by neighboring countries, such as Australia, warning those planning to travel to the region to take similar precautions. What is this virus, and why the multinational concern?
What is the JE Virus?
Japanese encephalitis virus (JE virus) is a member of the Flavivirus family, which includes Yellow Fever virus, West Nile virus, and Zika virus. It is endemic not only to Japan, but also throughout Southeast Asia and Oceana. It is transmitted by mosquitoes, most commonly the Culex mosquito, and can also reside in reservoir animals such as wild birds and pigs. When humans are bitten and infected, roughly 1/100 to 1/1000 will become symptomatic, with an estimated 68,000 symptomatic human cases occurring every year. Symptomatic individuals may initially only show mild, nonspecific symptoms such as headache, fever, and vomiting, but 1 in 250 infected individuals will quickly progress to develop encephalitis (or inflammation of the brain) resulting in altered mental status, seizures, coma, and even death. Of those that display symptoms, there is a 20-30% case fatality rate, and risk for future neurological deficits—such as intellectual deficits, paralysis, or seizures—is as high as 30-50%.
Prevention and Vaccination
A virus with this kind of deadly potential is obviously treated very seriously. Japan conducts regular screenings for antibodies in piggeries, and warning statements are issued once there is a positive result, often annually during the summer months. Citizens and travelers to endemic regions are advised to take general precautions against mosquito bites, such as wearing long-sleeve shirts and pants, applying insect repellent, and avoiding areas of stagnant water (where these insects prefer to breed). There are several vaccines against the virus employed worldwide, and it is estimated that over 300,000 infections have been avoided over the past decade due to use of vaccines. There is currently one FDA-approved vaccine available in the United States. This vaccine, called IXIARO, is recommended for anyone planning to travel or live in a JE virus-endemic country for longer than 1 month.
Taylor is a medical student at the University of Texas Medical Branch in Galveston. She is hoping to pursue her interest in infectious diseases by specializing in Internal Medicine or Pathology.
Sources:
Campbell, G., Hills, H., Fischer, M., Jacobson, J., Hoke, C., Hombach, J., Marfin, A., Solomon, T., Tsai, T., Tsu, V., & Ginsburg, A. (2011). Estimated global incidence of Japanese encephalitis: a systematic review. Bulletin of the World Health Organization, 89:766-774E.
CDC. Japanese Encephalitis Virus. 2023.
Moore, S. (2021). The current burden of Japanese encephalitis and the estimated impacts of vaccination: Combining estimates of the spatial distribution and transmission intensity of a zoonotic pathogen. PLoS Neglected Tropical Diseases, 15(10), e0009385.
Shimbun, K.N. (2023). Japanese encephalitis warning issued throughout Kumamoto Prefecture.
Thomson, T., Marsland, M., Minko, C., Snow, K., & Friedman, N. (2023). Japanese encephalitis: A rapid review of reported prevalence of infection, clinical disease and sequelae in immunologically naive populations to inform Australia’s response. Australian and New Zealand Journal of Public Health, 47:2.
Wang, X., Su, L., Sun, S., Hu, W., Mu, Q., Liang, X., Jin, N., Dai, T., Li, H., & Zhuang, G. (2021). Long-Term Neurological Sequelae and Disease Burden of Japanese Encephalitis in Gansu Province, China. Annals of global health, 87(1), 103.