Abstract
ObjectiveEnterovirus 71 (EV71) is causing life-threatening outbreaks in tropical Asia. In Taiwan and other tropical Asian countries, although nationwide EV71 epidemics occur cyclically, age-specific incidence rates of EV71 infections that are critical to estimate disease burden and design vaccine trials are not clear. A nationwide EV71 epidemic occurred in 2008–09 in Taiwan, which provided a unique opportunity to estimate age-specific incidence rates of EV71 infections.Study DesignWe prospectively recruited 749 healthy neonates and conducted follow-ups from June 2006 to December 2009. Sera were obtained from participants at 0, 6, 12, 24, and 36 months of age for measuring EV71 neutralizing antibody titers. If the participants developed suspected enterovirus illnesses, throat swabs were collected for virus isolation.ResultsWe detected 28 EV71 infections including 20 symptomatic and 8 asymptomatic infections. Age-specific incidence rates of EV71 infection increased from 1.71 per 100 person-years at 0–6 months of age to 4.09, 5.74, and 4.97 per 100 person-years at 7–12, 13–24, and 25–36 months of age, respectively. Cumulative incidence rate was 15.15 per 100 persons by 36 months of age, respectively.ConclusionsRisk of EV71 infections in Taiwan increased after 6 months of age during EV71 epidemics. The cumulative incidence rate was 15% by 36 months of age, and 29% of EV71 infections were asymptomatic in young children.
Highlights
Enterovirus 71 (EV71) was first isolated in California, USA, in 1969
Risk of EV71 infections in Taiwan increased after 6 months of age during EV71 epidemics
The cumulative incidence rate was 15% by 36 months of age, and 29% of EV71 infections were asymptomatic in young children
Summary
Enterovirus 71 (EV71) was first isolated in California, USA, in 1969. Since EV71 has been identified globally. Two patterns of EV71 outbreaks have been reported: small-scale outbreaks with few CNScomplicated cases and deaths, and large-scale outbreaks with frequent CNS-complicated cases and deaths [1]. The latter pattern occurred in Bulgaria, with deaths in 1975 [5]; in Hungary, with deaths in 1978 [6]; in Malaysia, with 29 deaths in 1997 [7]; in Taiwan, with 78 deaths in 1998 [8]; in Singapore, with 5 deaths in 2000 [9]; and recently in China, with more than 100 deaths in 2007, 2008, and 2009 [10,11,12]. Since the 1998 epidemic, EV71 has continued to cause nationwide epidemics again in 2000–2001, 2004–2005, and 2008–2009 in Taiwan [12,13,14,15,16,17,18,19,20,21,22]
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