Cholera is typically considered endemic in West Africa, especially in the Republic of Guinea. However, a three-year lull period was observed from 2009 to 2011, before a new epidemic struck the country in 2012, which was officially responsible for 7,350 suspected cases and 133 deaths. To determine whether cholera re-emerged from the aquatic environment or was rather imported due to human migration, a comprehensive epidemiological and molecular survey was conducted. A spatiotemporal analysis of the national case databases established Kaback Island, located off the southern coast of Guinea, as the initial focus of the epidemic in early February. According to the field investigations, the index case was found to be a fisherman who had recently arrived from a coastal district of neighboring Sierra Leone, where a cholera outbreak had recently occurred. MLVA-based genotype mapping of 38 clinical Vibrio cholerae O1 El Tor isolates sampled throughout the epidemic demonstrated a progressive genetic diversification of the strains from a single genotype isolated on Kaback Island in February, which correlated with spatial epidemic spread. Whole-genome sequencing characterized this strain as an “atypical” El Tor variant. Furthermore, genome-wide SNP-based phylogeny analysis grouped the Guinean strain into a new clade of the third wave of the seventh pandemic, distinct from previously analyzed African strains and directly related to a Bangladeshi isolate. Overall, these results highly suggest that the Guinean 2012 epidemic was caused by a V. cholerae clone that was likely imported from Sierra Leone by an infected individual. These results indicate the importance of promoting the cross-border identification and surveillance of mobile and vulnerable populations, including fishermen, to prevent, detect and control future epidemics in the region. Comprehensive epidemiological investigations should be expanded to better understand cholera dynamics and improve disease control strategies throughout the African continent.
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机译：霍乱通常被认为是西非的地方病，尤其是在几内亚共和国。但是，从2009年到2011年，这个国家经历了三年的平静期，之后该国在2012年爆发了新的流行病，该流行病正式造成7350例可疑病例和133例死亡。为了确定霍乱是从水生环境中重新出现还是由于人类迁徙而被进口，进行了全面的流行病学和分子调查。对国家病例数据库的时空分析建立了位于几内亚南部沿海的卡巴克岛（Kaback Island），将其作为2月初流行病的最初重点。根据现场调查，发现该指数病例是一名渔夫，他是最近从邻国塞拉利昂的沿海地区抵达的，该国最近发生了霍乱疫情。在整个流行期间取样的38例临床霍乱弧菌O1 El Tor分离株的基于MLVA的基因型作图表明，该菌株于2月在Kaback Island上分离的单一基因型的菌株具有逐步的遗传多样性，这与空间流行病传播有关。全基因组测序将该菌株鉴定为“非典型” El Tor变体。此外，基于全基因组的SNP系统发育分析将几内亚菌株归为第七次大流行的第三波的新进化枝，这与先前分析的非洲菌株不同，并且与孟加拉国分离株直接相关。总体而言，这些结果高度表明，2012年几内亚流行病是由霍乱弧菌克隆引起的，该克隆很可能是由感染者从塞拉利昂进口的。这些结果表明，促进跨境识别和监测包括渔民在内的流动人口和脆弱人群的重要性，以预防，发现和控制该地区未来的流行病。应该扩大综合的流行病学调查范围，以更好地了解霍乱的动态并改善整个非洲大陆的疾病控制策略。
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