On June 5, 2012, the Taiwan Centers for Disease Control (Taiwan CDC) announced four new cases of Japanese encephalitis in Taiwan. They developed their disease between May 17 and 29. The cases are two males and two females who respectively aged 40, 46, 48 and 74. They are either unvaccinated or with unknown vaccination history. They all reside in Tainan City. In addition, either their residence or workplace is adjacent or near to locations prone to vector breeding such as pig farms, pigeon farms, ponds or egret’s nests. Thus far, an accumulative total of five confirmed Japanese encephalitis cases have been reported and they all reside in Tainan City. Of the cases, three have been discharged and two are still hospitalized for medical treatment. As we have entered the Japanese encephalitis season in Taiwan, Taiwan CDC urges the public to take preventive measures against mosquito bites and receive appropriate vaccinations in a timely fashion in order to prevent transmission of the disease effectively.

According to Taiwan CDC’s surveillance data, transmission of Japanese encephalitis in Taiwan occurs annually between May and October and it usually peaks between June and July. Since the implementation of Japanese encephalitis vaccination in Taiwan in 1968, the average number of Japanese encephalitis cases confirmed each year is around 20~40, including 0-2 deaths, over the past decade. The average age of the cases is above 20 years old. The incubation period for Japanese encephalitis is generally 5-15 days. In severe cases, psychological or neurological sequelae, and even death may occur. The primary vector of Japanese encephalitis is a species of mosquito, Culex tritaeniorhynchus. Pigs act as the amplifying host for Japanese encephalitis. The vector mosquitoes are most active during dawn and dusk. To prevent further spread of the disease, health authorities will further reinforce promotion activities and install mosquito killer lights in highly endemic areas. In addition, Taiwan CDC urges physicians to remain vigilant against Japanese encephalitis and report a patient to the health authority if he/she develops suspected symptoms.

Japanese encephalitis vaccine has been proven the most effective in preventing Japanese encephalitis. To maximize the effect of prevention, vaccination is mostly available from March to May every year and can be extended to September depending on the number of vaccines available. A 2-dose regimen for routine childhood Japanese encephalitis vaccination is recommended for all toddlers aged 15 months and the 2 doses should be given two weeks apart. A booster dose should be given one year after the 2-dose primary vaccination. A second booster should be administered when the child attends first grade at elementary school. Although the Japanese encephalitis vaccination coverage rate in Taiwan is above 90%, some infants and children remain unvaccinated. Parents are urged to make sure their children are vaccinated against Japanese encephalitis at local health centers or designated hospitals. Beginning 2013, children aged above 5 is recommended another booster dose before starting elementary school. Adults who are at risk for Japanese encephalitis infection can consider receiving self-paid vaccines (approximately NT$250~500) at one of the 22 general hospitals in the nation, National Taiwan University Hospital Yun-Lin Branch, or National Yang-Ming University Hospital.

As the Japanese encephalitis season is upon us and the vector mosquitoes are most active during the summer months, Taiwan CDC reminds the public to avoid mosquito bites by limiting visits to vector-prone areas such as pig and other animal farms. If, however, visits to vector-prone areas are unavoidable, please wear light-colored clothing, long sleeves and long pants and apply officially approved mosquito repellent to exposed parts of the body to prevent mosquito bites and lower the risk of infection. For any questions or further information on Japanese encephalitis, please call the toll-free Communicable Disease Case Reporting and Consultation Hotline 1922, or 0800-024582 if calling from a cell phone, or visit the Taiwan CDC’s website: http://www.cdc.gov.tw.