The enterovirus 71 epidemic in 2008--public health implications for Hong Kong

Abstract

Objectives: We compared the epidemiological, clinical and laboratory characteristics of enterovirus 71 (EV71) cases recorded in the epidemic year of 2008 with those of the past decade.

Methods: We estimated the annual incidence rates in the general population and in different age groups. We reviewed the clinical and epidemiological information of the cases. The complication and case fatality rates (CFR) were compared with the corresponding average rates for the period 1998-2007. The molecular strains of EV71 isolates were determined.

Results: The estimated annual incidence was 1.4/100,000 in the general population, with the highest incidence (27.9/100,000) reported among children aged under 5 years. The seasonal peak occurred from May to July. The majority (92.9%) presented with hand-foot-mouth disease (HFMD; 90.8%) or herpangina, and 11.2% had complications including meningitis or encephalitis (6.1%), pneumonia (3.1%), acute flaccid paralysis (1.0%), and shock (1.0%). The CFR was 1.0%. Nearly half (45.9%) of school-aged cases had concurrent HFMD outbreaks at their schools/institutions. There was no statistically significant difference in the complications rate and CFR when compared to those of the past decade. Molecular analysis showed that the majority were genogroup C4 strains, similar to the past circulating strains.

Conclusions: The cyclical high activity has had significant public health and social implications. To strengthen public health surveillance and control, EV71 infection was made a statutory notifiable disease in 2009.