Reemergence of Japanese Encephalitis in South Korea, 2010-2015.

Abstract

To the Editor: Japanese encephalitis (JE) is caused by a virus transmitted by Culex tritaeniorhynchus mosquitoes. JE was the major public health concern in South Korea until the late 1960s, with several thousand cases reported annually. The national vaccination program with the inactivated mouse brain–derived Nakayama strain was initiated in 1983 and targeted children <15 years of age. During 1983–2000, annual booster vaccinations were given to children <15 years of age, but in 2000, the booster schedule was changed to 2 doses (1 dose each) for children 6 and 12 years of age. The live attenuated JE vaccine SA 14-14-2 was introduced in 2002 and included in the national immunization program in 2014. After introduction of the mandatory immunization program, JE was nearly eliminated; during most of the past 3 decades, <0.02 cases per 100,000 population have been reported annually (1). However, since 2010, JE has reemerged in South Korea. We describe epidemiologic data for JE, focusing on the recent increase in number of cases in South Korea. We accessed demographic information from the disease web statistics system provided by the Korea Centers for Disease Control and Prevention (2). Our study was exempted from review by the Institutional Review Board at Seoul National University Hospital (E-1602-053-739).