Surveillance results of acute flaccid paralysis in Chongqing from 2004 to 2007

Objective　The study was conducted to evaluate the performance of surveillance on acute flaccid paralysis (AFP) in Chongqing from 2004 to 2007. Methods　The viruses were isolated and identified according to Polio Laboratory Manual. PCR RFLP and ELISA were applied in intratypic differentiation of the isolates by National Poliomyelitis Laboratory. Results　A total of 12 strains of poliovirus (PV) were isolated from the stool samples of 395 AFP patients，including 1 strain of type Ⅰpoliovirus，4 strains of type Ⅱ poliovirus，4 strains of type Ⅲ poliovirus，1 strain of mixed poliovirus and 2 strains of poliovirus mixed with NPEV (non polio enterovirus). All PVs were sent to National Poliomyelitis Laboratory for intratypic differentiation and were subsequently identified as vaccine related strains. No vaccine derived poliovirus（VDPV）were detected. A total of 27 strains of non polio enterovirus were isolated. Conclusion　No wild poliovirus or vaccine derived poliovirus was found in the AFP cases in Chongqing from 2004 to 2007. The performance of AFP surveillance system proved to meet the control requirements, suggesting a stable performance of the poliomyelitis laboratory in Chongqing. Therefore, it is suggested that laboratory surveillance should be strengthened to ensure the high sensitivity of the surveillance.