贵州省2004年一起疫苗衍生株脊髓灰质炎病毒流行的调查分析

目的证实2004年贵州省贞丰县发生的Ⅰ型疫苗衍生株脊髓灰质炎（脊灰）病毒循环（cVDPVs），分析cVDPVs发生原因，及时发现脊灰野病毒（wild—poliovirus）、疫苗衍生株脊灰病毒（VDPVs）和临床相似症状的其他脊灰疫苗相关株病毒。方法对疫区进行流行病学现场调查，采集急性弛缓性麻痹（AFP）病例及密切接触者粪便标本进行脊灰病毒（PV）分离鉴定与基因序列测定，并对贞丰县近几年报告AFP病例及接触者粪便标本病毒学监测结果进行分析。结果从贞丰县挽澜乡2例AFP病例和3名密切接触者粪便标本中分离到Ⅰ型VDPVs；发生Ⅰ型cVDPVs事件后，5例诊断为临床符合脊灰的AFP病例中有3例分离到Ⅰ型或Ⅱ型脊灰疫苗相关株病毒；病毒学监测结果显示，贞丰县人群中肠道病毒阳性检出率（55．1％）明显高于贵州全省水平（23．2％），2004年PV分离率（36．8％）明显高于往年，16株PV中Ⅰ型所占比例（43．8％）明显高于贵州全省平均水平（18．3％）。结论脊灰Ⅰ型VDPVs已经在贞丰县引起了循环（cVDPVs）；人群中PV和非脊灰肠道病毒带毒率明显增高及疫苗接种率严重低下，是该次Ⅰ型cVDPVs发生的原因；应加强无脊灰状态下疫苗接种率的评估和早期疫情预测工作。

Study on an epidemic caused by the vaccine-derived poliovirus circulation in Guizhou province, 2004

OBJECTIVE: To study the circulating vaccine-derived poliovirus (cVDPVs) that occurred in Zhenfeng county, Guizhou province in 2004 and to discover wild-poliovirus, vaccine-derived poliovirus (VDPVs) and other vaccine-associated poliovirus which could cause clinical poliomyelitis. METHODS: Field epidemiological studies at the epidemic area and collecting acute flaccid paralysis (AFP) case and contact stool specimen for virus identification and nucleotide sequencing. Analysis on data related to annual reports on stool specimens surveillance which involved AFP case and contacts in the resent years in Zhenfeng county. RESULTS: Type-I VDPVs had been isolated from 2 AFP cases and 3 contact stool specimen in Wanlan village of Zhenfeng. After the first cVDPVs case was identified, there were 3 cases identified of having other vaccine-associated poliovirus of type-I or type-II in the 5 case of AFP that met the criteria of clinical poliomyelitis. The result of virological surveillance on polio showed that the EV isolation rate (55.1%) of Zhenfeng county was higher than the rate from the whole province of the same year (23.2%). The poliovirus (PV) isolation rate (36.8%) was obviously higher in 2004 than in the previous years. In the 16 PVs strains, the type-I accounted for 43.8% which was significantly higher than the average level (18.3%) from the whole province. CONCLUSIONS: Data indicated that the type-I VDPVs had been circulating (cVDPVs) in Zhenfeng county in Guizhou province. Clinical poliomyelitis was caused by non-VDPVs. The increased PV infection and the decreasing rate of vaccination in the general population were responsible for the epidemic of type-I cVDPVs at this time. Monitoring and evaluation on the rate of routine immunization program and prediction of the trend of epidemic should be strenthened.