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Volume 32, Number 6—June 2026
Dispatch
Repeated Extraneous Introductions of Cholera, Thailand, 2007–2025
, Amonrattana Roobthaisong, Warawan Wongboot, Pawinee Doung-ngern, Wichan Bhunyakitikorn, Pilailuk A. Okada, Thanee Wongchai, Witaya Swaddiwudhipong, Tetsuya Iida, and Shigeyuki Hamada
Table
Single-nucleotide polymorphism differences between Thailand outbreak clusters and the most closely related non-Thailand strains from study of repeated extraneous introductions of cholera, Thailand, 2007–2025*
| Lineage (cluster) | SNP range within cluster | Closest non-Thailand strains | Origin, country/year | SNPs from Thailand isolate |
|---|---|---|---|---|
| TH1 (a) | 0–7 | MAB004 | Bangladesh/2005 | 7 |
| MAB006 | Bangladesh/2005 | 8 | ||
| 4488 | India/2006 | 13 | ||
| THSTI_J4770 | India/2004 | 13 | ||
| BGD005 |
Bangladesh/2007 |
13 |
||
| TH1 (b) | 0–7 | MAB004 | Bangladesh/2005 | 9 |
| MAB006 | Bangladesh/2005 | 12 | ||
| 4488 | India/2006 | 17 | ||
| THSTI_J4770 | India/2004 | 17 | ||
| BGD005 |
Bangladesh/2007 |
17 |
||
| TH2 (c) | 0–21 | THSTI_K9398 | India/2005 | 12 |
| MAB001 | Bangladesh/2004 | 13 | ||
| CNRVC060089 | India/2006 | 13 | ||
| CNRVC060333 | India/Nepal/2006 | 13 | ||
| MBN17 |
India/2004 |
14 |
||
| TH3 (d) | 0–14 | PCS-0023 | Bangladesh/2010 | 6 |
| IDH-07956 | India/2015 | 7 | ||
| BGD133 | Bangladesh/2015 | 8 | ||
| HCIS-055B | Bangladesh/2013 | 10 | ||
| BGD128 |
Bangladesh/2015 |
10 |
||
| TH4 (e) | 0–5 | DMAVC-8 | Bangladesh/2022 | 5 |
| DMAVC-18 | Bangladesh/2022 | 5 | ||
| DMAVC-17 | Bangladesh/2022 | 7 | ||
| DMAVC-19 | Bangladesh/2022 | 7 | ||
| DMAVC-4 | Bangladesh/2022 | 8 |
*To identify the closest non-Thailand relatives, we calculated pairwise SNP distances for all 150 Thailand seventh pandemic isolates against the global dataset using snp-dists (https://github.com/tseemann/snp-dists). To capture the full genetic diversity, we compared each Thailand genome independently rather than using a single representative per cluster. For each cluster, we selected the 5 non-Thailand strains with the smallest SNP distances. SNP ranges within clusters reflect internal diversity, whereas differences from non-Thailand strains indicate potential geographic origins. SNP, single-nucleotide polymorphism.