Department of Virology, National Institute of Health, Chak Shahzad, Islamabad, Pakistan.
Clin Infect Dis. 2016 Jan 15;62(2):190-198. doi: 10.1093/cid/civ831. Epub 2015 Sep 28.
Despite tremendous efforts in the fight against polio, Pakistan bears the highest proportion of poliomyelitis cases among the 3 endemic countries including Afghanistan and Nigeria. Apart from insecurity and inaccessibility challenges, the substantial shift of unimmunized children from North Waziristan due to recent military operations was presumed to favor the widespread poliovirus infection in Pakistan.
To better understand the current epidemiological situation, we analyzed the virologic data of wild poliovirus type 1 (WPV1) strains detected in Pakistan during 2013-2015.
Five genetic clusters (A-E) were identified with at least 5% nucleotide divergence in the viral protein 1 (VP1) coding region. Peshawar, Quetta, and Karachi were found to be the major endemic foci where multiple discrete genetic lineages of WPV1 were detected. Phylogenetic analysis suggests that wild poliovirus strains from endemic regions were genetically distant (with 5%-15% VP1 nucleotide divergence) from those detected in North Waziristan cases, excluding the possibility of a recent progenitor of WPV1 instigating single-source transmission across the country. Orphan lineages detected in Rawalpindi, Lahore, Hyderabad, Sukkur, and Jacobabad revealed silent transmission and the need for vigilant surveillance. Sustenance of analogous genetic lineages over a period of 3 years highlights multiple unimmunized foci present to maintain viral genetic diversity.
Our findings are inconsistent with the hypothesis that impoverished populations from North Waziristan serve as a possible determinant of widespread poliomyelitis infection in Pakistan and further emphasize the need to scale-up clinical and environmental surveillance as well as immunization activities.
尽管在抗击脊灰炎方面做出了巨大努力，但巴基斯坦在包括阿富汗和尼日利亚在内的 3 个流行国家中脊灰炎病例比例最高。除了不安全和难以进入的挑战外，由于最近的军事行动，来自北瓦济里斯坦的未接种儿童大量转移，这被认为有利于巴基斯坦广泛的脊灰病毒感染。
为了更好地了解当前的流行病学情况，我们分析了 2013 年至 2015 年期间在巴基斯坦检测到的野生脊灰病毒 1 型（WPV1）毒株的病毒学数据。
在病毒蛋白 1（VP1）编码区至少有 5%核苷酸差异的情况下，确定了 5 个遗传簇（A-E）。白沙瓦、奎达和卡拉奇是主要的流行焦点，在那里检测到 WPV1 的多个离散遗传谱系。系统进化分析表明，来自流行地区的野生脊灰病毒株与在北瓦济里斯坦病例中检测到的病毒株在遗传上相距较远（VP1 核苷酸差异为 5%-15%），排除了 WPV1 的近期祖先在全国范围内引发单一来源传播的可能性。在拉瓦尔品第、拉合尔、海得拉巴、苏库尔和雅各布阿巴德检测到的孤立谱系表明存在沉默传播，需要进行警惕性监测。在 3 年的时间里，类似遗传谱系的维持突出了存在多个未接种的焦点来维持病毒的遗传多样性。
我们的发现与以下假设不一致，即来自北瓦济里斯坦的贫困人群可能是巴基斯坦广泛发生脊灰炎感染的一个决定因素，这进一步强调需要扩大临床和环境监测以及免疫接种活动。
