The changing seroepidemiology of enterovirus 71 infection among children and adolescents in Singapore

The survey involved the prospective collection of 1,200 residual sera from Singapore residents aged 1-17 years in two hospitals. Neutralizing antibodies to EV71 were detected by the microneutralization test. The geometric mean titer (GMT) of EV71 antibodies and 95% confidence intervals (CI) were calculated and compared by age groups. Statistical significance was taken as P < 0.05.The overall EV71 antibody prevalence was 26.9% (95% CI: 24.5-29.5%). It increased significantly from 14.3% in children aged 1-6 years to 27.8% in those aged 7-12 years, and reached 38.8% in adolescents aged 13-17 years. The seroconversion rate differed by about 12% between the consecutive age groups. The GMT of EV71 antibodies was higher among primary school children aged 7-12 years in our study than that among the 6-12 year age group in the 1996-1997 study.Higher antibody titers were observed in children aged 1-6 years than those in the other two age groups, indicating that most of the infections had been acquired during early childhood. EV71 infection is common among children and adolescents in Singapore, with 39% infected by the time they are in secondary school (13-17 years of age).Enterovirus 71 (EV71) and coxsackievirus A16 (CA16) have caused large epidemics of hand, foot and mouth disease (HFMD) worldwide. Since EV71 was first identified in 1969 from an infant suffering from encephalitis in California [1], outbreaks associated with this virus have been documented, including in Australia in 1972, Japan in 1973 and 1978 [2,3], Bulgaria in 1975 [4], and Hungary in 1978 [5]. EV71 infection is occasionally associated with severe complications (such as encephalitis) and deaths in children. Since 1997, EV71-related HFMD epidemics in the Asia-Pacific region have been increasingly reported, including in Sarawak, Malaysia in 1997 [6], 2000 [7,8], 2003 and 2006 [9]; Brunei in 2006 [10]; Perth, Australia in 1999 [11]; Taiwan in 1998 [12] and 2000 [13]; Japan in 2000 and 2003 [14]; and China in 2