Genomic Surveillance Points to Cholera Strains, Dynamics in Bangladesh Refugee Population

In a paper appearing in Nature Communications, researchers at the Wellcome Sanger Institute, the International Centre for Diarrhoeal Disease Research, and elsewhere assess cholera mass vaccination effects in a refugee population in Bangladesh where the cholera-causing bacteria Vibrio cholerae is endemic. Using whole-genome sequencing and genomic surveillance, the team assessed more than 200 V. cholerae samples collected from displaced Rohingya Muslim refugees at crowded settlements in southern Bangladesh's Cox's Bazar district from 2017 to 2019, revealing the presence of a highly virulent strain called 7PET as well as previously unappreciated 7PET substrains with global or regional distributions. Based on the detection of high-risk forms of V. cholerae at the Cox's Bazar refugee site considered, the authors suggest that broader epidemic spread of these bug may have been curbed through a mass vaccination campaign in 2017. "Here we show that as the pandemic V. cholerae lineage circulates in this vulnerable population, without a vaccine intervention, the risk of an epidemic was very high," they write, noting that the 7PET subclades identified "were associated with different disease patterns that could be partially explained by genomic differences."