Population genetics of Vibrio cholerae from Nepal in 2010: evidence on the origin of the Haitian outbreak - PubMed (original) (raw)

. 2011 Sep 1;2(4):e00157-11.

doi: 10.1128/mBio.00157-11. Print 2011.

Lance B Price, James M Schupp, John D Gillece, Rolf S Kaas, David M Engelthaler, Valeria Bortolaia, Talima Pearson, Andrew E Waters, Bishnu Prasad Upadhyay, Sirjana Devi Shrestha, Shailaja Adhikari, Geeta Shakya, Paul S Keim, Frank M Aarestrup

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Population genetics of Vibrio cholerae from Nepal in 2010: evidence on the origin of the Haitian outbreak

Rene S Hendriksen et al. mBio. 2011.

Abstract

Cholera continues to be an important cause of human infections, and outbreaks are often observed after natural disasters, such as the one following the 2010 earthquake in Haiti. Once the cholera outbreak was confirmed, rumors spread that the disease was brought to Haiti by a battalion of Nepalese soldiers serving as United Nations peacekeepers. This possible connection has never been confirmed. We used whole-genome sequence typing (WGST), pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing to characterize 24 recent Vibrio cholerae isolates from Nepal and evaluate the suggested epidemiological link with the Haitian outbreak. The isolates were obtained from 30 July to 1 November 2010 from five different districts in Nepal. We compared the 24 genomes to 10 previously sequenced V. cholerae isolates, including 3 from the Haitian outbreak (began July 2010). Antimicrobial susceptibility and PFGE patterns were consistent with an epidemiological link between the isolates from Nepal and Haiti. WGST showed that all 24 V. cholerae isolates from Nepal belonged to a single monophyletic group that also contained isolates from Bangladesh and Haiti. The Nepalese isolates were divided into four closely related clusters. One cluster contained three Nepalese isolates and three Haitian isolates that were almost identical, with only 1- or 2-bp differences. Results in this study are consistent with Nepal as the origin of the Haitian outbreak. This highlights how rapidly infectious diseases might be transmitted globally through international travel and how public health officials need advanced molecular tools along with standard epidemiological analyses to quickly determine the sources of outbreaks.

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Figures

FIG 1

FIG 1

Genetic relationships among V. cholerae isolates from Nepal and Haiti. A single maximum parsimony tree was reconstructed using 752 SNPs from 34 whole-genome sequences. There were 184 parsimony-informative SNPs, of which 6 were homoplastic, resulting in a CI of 0.97 (excluding uninformative characters). The branch lengths are labeled in red, and for branches affected by homoplasy, minimum and maximum branch lengths are designated. Members of SNP genotypic group V (16) are indicated. SNP differences among the three most closely related Nepali groups and the Haitian group are shown and characterized in Table S1 in the supplemental material.

FIG 2

FIG 2

Locations of the five districts in Nepal where the V. cholerae O1 Ogawa strains were isolated.

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