Korean J Pediatr 2010;53(5):616-622 • DOI: 10.3345/kjp.2010.53.5.616 617 Introduction On April 18 2009, a 21-month-old girl was referred to the pediatric emergency room of the Ewha Womans University Mokdong Hospital. She had progressive weakness of the lower limb, which had begun 3 days earlier. She was treated at the local hospital with the hand-foot-mouth disease (HFMD). Her consciousness was clear. She did not have any rash on the skin and showed asymmetric lower leg weakness with more severity on left leg. She was immunized with 3 doses of inactivated polio vaccine. On CSF examination, pleocytosis was noted, but chemistry profiles were normal. Because of her acute asymmetric flaccid paralysis of lower limb, her stool was sent to the Division of Enteric and Hepatitis Viruses, National Institute of Health, Korea Centers for Disease Control and Prevention under the impression of poliomyelitis-like paralysis due to enterovirus 71 (EV71). On her stool examination, EV71 with C1 type was discovered. She was the first confirmed case of enterovirus 71 infection on 2009 epidemics in Korea1). In the spring of 2009, a large nationwide outbreak of HFMD caused by HEV71 occurred in Korea (Fig. 1). Most of the cases were in children <6 years of age and one case was fatal. EV71 became an emerging concern in Korea. The purpose of this review is to overview the recent outbreaks of EV71 infection in Korea with exploring epidemiology, virology, clinical manifestations and management. Virus and genotypes The genus Enteroviruses are nonenveloped, single-stranded, positive-sense viruses in the Picornaviridae (“small RNA virus”) family. The human enteroviruses were originally classified echoviruses, coxsackieviruses, polioviruses by their replication Fig. 1. Weekly distribution of enterovirus infection in 2009, Korea. patterns in tissue culture and animals. Recently they have been reclassified based on molecular properties into 5 species, polioviruses, human enterovirus A, human enterovirus B, human enterovirus C, and human enterovirus D. EV71 discovered in California in 19692) belongs to the human enterovirus A3). In recent epidemics in the Asia-Pacific region, the predominant EV71 genotypes were various. In Sarawak during 1997 and Singapore during 1998, genotype B3 was most prevalent. EV71 isolated from patients in the Taiwanese epidemic during 1998 belonged to genotype C24, 5). During the epidemics in Malaysia and Singapore in 2000, the predominant genotype was B45). And, the EV71 outbreaks in Brunei, Sarawak and Singapore in 2006 were caused by subgenogroup B5 virus6). EV71 in the outbreak in China during 2007-2008 belonged to subgenotype C4a7, 8). The increasing fatality of EV71 infection in recent epidemics has been thought to be due to both endemic and epidemic circulation of the virus and its evolution. The possible occurrence of inter-typic recombination of EV71 may play important roles in the emergence of various EV71 subgenotypes with varied virulence and clinical manifestations9). Since 2000, the laboratory surveillance system for early detection of EV71 has been operating in Korea. On 2000, EV71 were isolated for the first time from 12 patients with HFMD in Korea. They belonged to genotype C3, which has been identified rarely in other epidemics in recent years4, 10). During outbreaks in China in 2008-2009, the most frequent genotype among the EV71 strains isolated from patients was C4a. Genotype C1 viruses were isolated from cases of uncomplicated HFMD in Singapore and Sarawak during 1998 and in Sarawak and Western Australia during 2005, 11). It does not appear that a single neurovirulent genotype is associated with the severe and fatal cases12). Further study is needed to elucidate the factors influencing the virulence of EV71. Epidemiology EV71 infection has the seasonal distribution of a peak in the spring and summer months. The transmission of enterovirus occurs within families, daycare centers, playgrounds and hospital nurseries. More children would be congregating in a limited space, which provides a readily available reservoir for the rapid circulation of the virus13). The fecal-to-oral route is considered a major transmission route. Long periods of viral shedding may account for the widespread transmission of EV7114). Chung et al15) demonstrated that EV71 is excreted through the stool of infected patients for up to 6 weeks. Chang et al16) presented that the culture-positive rate of throat swabs was higher than that of