Detection of acute flaccid paralysis (AFP) cases and poliovirus in Shaanxi province

Objective To analyze the epidemiological character of AFP cases and to detect poliovirus in Shaanxi province during 2003-2008 in order to increase the sensitivity of vaccine-derived poliovirus(VDPVs) surveillance.Methods Epidemiological analysis was conducted in AFP cases with positive poliovirus detection and VP1 genomic sequencing technique was used to analyze the molecular character of vaccine-variant polioviruses.Results From 2003 to 2008,29 poliovirus strains were isolated from AFP cases,and the number of type Ⅱ strains exceed to the summation of type Ⅰ and type Ⅲ strains.75.86% of cases were children.The main paralysis parts of body were single or both lower extremity and limbs.Fourteen strains were indentified as vaccine-variant poliovirus.The variant rate of VP1 sequence did not reach 1%.Among these cases,7 cases were not fully vaccinated children and 9 were under 2 years old.Conclusion VDPV emergence and cVDPVs circulation still possibly occur in course of polio-eradication.It is important to keep high-level surveillance and vaccination coverage.