Reemerging of enterovirus 71 in Taiwan: the age impact on disease severity.

Enterovirus 71 (EV71) infection commonly strike children under the age of 3 years, with an occasionally unfavorable outcome in children. This study was designed to explore the relationship between age and the severity of complications, which may associate with antibody-dependent enhancement (ADE) in EV71. All EV71-infected patients during the outbreak of 2008 were recruited. In total, 134 patients were enrolled and categorized into two age groups, 0-12 months (n = 18) and >12 months (n = 116). Pulmonary edema/hemorrhage more commonly occur in patients younger than 12 months. No difference in the occurrence of herpangina/hand-foot-and-mouth disease (HFMD), uncomplicated brainstem encephalitis (BE), or autonomic nervous system (ANS) dysregulation was noted between the two age groups. Patients with pulmonary edema/hemorrhage (11.9 ± 14.7 months) were younger than patients with herpangina/HFMD (35.8 ± 26.4 months) or ANS dysregulation (33.9 ± 20.9 months). Our findings are in agreement with the data regarding the outbreak in Taiwan, in which a decrease in age corresponded to an increase in disease severity with regard to central nervous system complications. A reduction of maternal antibodies to the subneutralizing level within 1 year of age may be associated with the ADE of the infection. This study could provide possible clinical significance with regard to ADE phenomena in young infants infected by EV71.