Japanese encephalitis
什麼是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.
您如何獲得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.
易感性和抵抗力
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.
有哪些症狀？
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.
預防措施
旅行者感染日本腦炎病毒的風險非常低。但是，可以接種疫苗。美國疾病控制和預防中心疫苗接種實踐諮詢委員會建議日本腦炎 （JE） 疫苗接種人員前往 JE 流行國家居住，以長期居住（例如，大於或等於一個月）前往 JE 流行地區的旅行者和經常前往 JE 流行地區的旅行者。
根據計畫的旅行持續時間、季節、位置、活動和住宿情況，對於短期（例如，少於一個月）風險增加的旅行者，以及前往 JE 流行地區的旅行者，也應考慮接種 JE 疫苗。不確定其特定的旅行持續時間、目的地或活動。
不建議患有低風險行程的旅行者接種 JE 疫苗，例如僅限於城市地區或明確定義的 JE 病毒傳播季節以外的短期旅行。
避免蚊子接觸也是一項重要的預防措施。使用帶有 30%-50% DEET 的驅蟲劑（蟲噴霧）和在戶外穿長袖襯衫、長褲和帽子，防止蚊蟲叮咬，尤其是在農村地區的叮咬高峰期。
治療
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.
疫苗接種
通常在哪裡發生？
日本腦炎發生在印度和整個亞洲大部分地區（特別是中國、日本、韓國、俄羅斯東部、越南、泰國、老撾、馬來西亞、印尼、柬埔寨和西太平洋的一些島嶼）。在非洲、歐洲或美洲尚未發現。
