Japanese encephalitis
什么是Japanese encephalitis？
Japanese encephalitis is an acute inflammatory viral disease of short duration that involves parts of the brain, spinal cord, and meninges (linings of the brain). It is closely related to West Nile virus, St. Louis Encephalitis virus, and other encephalitic viruses (viruses that affect the brain). Japanese encephalitis disease is caused by the mosquito-borne Japanese encephalitis virus.
The risk to short-term travellers and those who confine their travel to urban centres is very low. Expatriates and travellers living for prolonged periods in rural areas where Japanese encephalitis is endemic or epidemic are at greater risk. Travellers with extensive outdoor, evening and night-time exposure in rural areas (for example, while bicycling, camping, working outdoors, or sleeping in unscreened structures without bed nets) may be at high risk even if their trip is brief. Transmission is seasonal and occurs in the summer and autumn in the temperate regions. Sometimes the transmission season extends or varies with the rainy season and irrigation practices. In tropical parts of Asia, mosquitoes that breed in rice paddies may also be important vectors, and Japanese encephalitis virus transmission may occur over a longer season or even throughout the year.
如何获得Japanese encephalitis？
Japanese encephalitis is transmitted through the bite of certain kinds of infected mosquitoes. The most common infected mosquito feeds outdoors from dusk to dawn in mainly rural agricultural areas, such as rice fields, marshes, and other small stable collections of water found around cultivated fields. Japanese encephalitis cannot be transmitted person to person.
易感性和抗性
Susceptibility to Japanese encephalitis disease is usually highest in infancy and old age. Once infected, a person obtains lifelong immunity. In highly endemic areas, adults are largely immune to local strains because they have already had a mild or unapparent infection.
症状是什么？
The majority of human Japanese encephalitis viral infections do not show any symptoms, and only about 1 in 250 of those infected will develop symptoms of the disease. Japanese encephalitis usually begins with the sudden onset of fever with gastrointestinal symptoms and headache. Encephalitis (inflammation in the brain) is the most common manifestation of the infection. Mental or behavioural changes, neurologic deficits, generalized weakness, and movement disorders may develop after the onset of encephalitis. Seizures are fairly common among children. Milder forms of the disease, such as aseptic meningitis (inflammation of the lining of the brain without an identifiable bacteria or virus) or fever with headache, can occur more commonly among adults.
预防措施
旅行者感染日本脑炎病毒的风险非常低。但是，可以接种疫苗。美国疾病控制和预防中心疫苗接种实践咨询委员会建议日本脑炎 （JE） 疫苗接种人员前往 JE 流行国家居住，以长期居住（例如，大于或等于一个月）前往 JE 流行地区的旅行者和经常前往 JE 流行地区的旅行者。
根据计划的旅行持续时间、季节、位置、活动和住宿情况，对于短期（例如，少于一个月）风险增加的旅行者，以及前往 JE 流行地区的旅行者，也应考虑接种 JE 疫苗。不确定其特定的旅行持续时间、目的地或活动。
不建议患有低风险行程的旅行者接种 JE 疫苗，例如仅限于城市地区或明确定义的 JE 病毒传播季节以外的短期旅行。
避免蚊子接触也是一项重要的预防措施。使用带有 30%-50% DEET 的驱虫剂（虫喷雾）和在户外穿长袖衬衫、长裤和帽子，防止蚊虫叮咬，尤其是在农村地区的叮咬高峰期。
处理
Among patients with encephalitis symptoms, approximately 20%-30% of patients die, and 30%-50% of survivors have neurologic, cognitive, or behavioural disabilities. There is no specific antiviral treatment for Japanese encephalitis. Therapy consists of supportive care, treatment of symptoms, and management of complications.
疫苗接种
它常见于哪里？
日本脑炎发生在印度和整个亚洲大部分地区（特别是中国、日本、韩国、俄罗斯东部、越南、泰国、老挝、马来西亚、印度尼西亚、柬埔寨和西太平洋的一些岛屿）。在非洲、欧洲或美洲尚未发现。
