We performed preepidemic and postepidemic serological surveys to elucidate the rate of enterovirus 71 (EV71) infection in Lu'an City, Anhui Province, Central China. For the preepidemic study, a total of 472 healthy infants and children (age range, neonates to 15 years) were randomly selected before the 2008 outbreak of EV71 in the region. Blood samples were collected and tested for neutralizing antibodies (NAbs) against EV71 by performing a microneutralization assay. The results of preepidemic

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... erological survey showed that 43.2z (204/472) of the tested samples yielded positive results for NAbs against EV71. The seropositivity rates were 29.6z (93/314) in children who were 0-7 years of age and 74.6z (59/79) in children who were 12-15 years of age. The overall geometric mean titer was 18.1, and the highest antibody titers were detected in children who were 5-7 years of age; this suggests that this group was frequently exposed to EV71 infection. For the postepidemic study, 83 serum samples were collected from healthy children Ã15 years of age in 2010. The seropositivity rate of EV71 NAbs increased in this young population after the 2008 outbreak, especially in 2-to 11-year-old children. This report shows that EV71 was spreading in Lu'an City before the 2008 outbreak, and children under 7 years of age were the main susceptible population.