OBJECTIVEIt was noticed that coxsackievirus A16 (CA16) and enterovirus 71 (EV71) were two major etiological agents of hand, foot and mouth disease (HFMD) in children. Recently there were several large outbreaks of HFMD in the Asia-Pacific region, and there was a propensity to cause severe complications or death in children under 5 years of age. The severe forms were associated with EV71 infection. Although epidemics of HFMD have been reported in the mainland of China, few reports about EV71 as the pathogen of HFMD epidemics are available. The present study was conducted to investigate the causal agent of an HFMD epidemic in children in Shanghai from April to June of 2002.

METHODSTotally 102 specimens (including vesicle fluid, stool and throat swabs) were collected from 72 patients with HFMD. The specimens were inoculated into Vero and/or RD cells. At first all the isolates were respectively neutralized by the RIVM pools of enterovirus antiserum, the type-specific antisera to EV71 or to CA16. Secondly all untyped isolates were tested by RT-PCR assay with two specific primer pairs for VP1 genes of EV71 and CA16 respectively. The EV71 and CA16 were identified depending on the size of PCR products. Sequence analyses of VP1 genes of 9 virus strains were performed by the laboratory of China CDC.

RESULTSViruses were isolated from 91 specimens from 67 patients. Serotyping by neutralization failed for all the isolates. But the RT-PCR results indicated that the viruses isolated from 78 specimens from 58 patients were identified as positive for CA16 and the isolates from 13 specimens from 9 patients were identified as positive for EV71, the ratio between CA16 and EV71 was 6.4:1. The results of sequence analyses were consistent with those of PCR assay. Two EV71 strains isolated in this study belonged to a new lineage (C4) within genogroup C. One patient with EV71-associated HFMD had a complication of encephalitis with convulsion, shock, coma and dyspnea.

CONCLUSIONCA16 and EV71 were the primary causes of HFMD during the epidemic. It was the first report of EV71-associated severe encephalitis occurred in patients with HFMD in Shanghai.