Background: Few studies have investigated the viral isolation characteristics for severe complicated enterovirus infection (SCEI). This study evaluated the seasonality and contribution of circulated viruses to the chronologic trend and weekly reported SCEI epidemic.
Methods: Enterovirus infection surveillance and virology laboratory data in 2000 to 2008 obtained from the Centers for Disease Control in Taiwan were analyzed. We measured the monthly and weekly virology isolation rates by viral types. The virus-specific and the season-specific relative risks for SCEI and 95% confidence intervals (CI) associated with the isolated circulating viruses and weather status was evaluated.
Results: Among 1539 virology confirmed SCEI cases, the mean annual incidence rates ranged from 0.72/100,000 to 32.5/100,000 in children aged 5 years and less; rates were higher in warm months with cases peaking in June (12.6%). The untypeable nonpolio enterovirus was the most frequently isolated type among the monitored specimens (6.07%), followed by coxsackievirus A (3.99%), EV71 (1.77%), coxsackievirus B (1.56%), and echovirus (1.23%). However, these SCEI cases had very strong associations with the isolation of EV71 and coxsackievirus A and B. The corresponding relative risks were 1.14 (95% CI, 1.11-1.17), 1.03 (95% CI, 1.01-1.04), and 1.09 (95% CI, 1.07-1.12), respectively, for 1% increase in weekly isolation rate.
Conclusions: Isolation rates for EV71 and coxsackieviruses A and B can predict the development of SCEI cases, particularly in warm months.