Background & objectives: Atypical El Tor strains of Vibrio cholerae are frequently implicated in outbreaks of cholera. It is important to understand genetic variations of such strains which impact clinical and epidemiological outcomes. The present study was carried out to characterize an outbreak of cholera which occurred between July 8 and 13, 2018, in a remote settlement in Nashik district, Maharashtra.
Methods: A large number of acute diarrhoea cases were reported in Rahude village, Nashik, Maharashtra since July 8, 2018. Molecular characterization of the isolated strains of V. cholerae was done.
Results: 195 cases of cholera were detected from a population of 850 (attack rate 22.9%) with two deaths (Case Fatality Ratio of 1.03). A non-haemolytic polymyxin B sensitive strain of V. cholerae O1 Ogawa was isolated from 5/14 fecal samples. Molecular characterization of the isolates indicated that this strain was an altered El Tor (AET) strain. Deletion of the trinucleotide 'GTA' in the rstB gene, a unique feature of classical strains, was observed.
Interpretation & conclusions: A cholera outbreak caused by a non-haemolytic polymixin B sensitive AET strain, occurred from July 8 to 13, 2018, in a remote settlement in western India. The molecular characterization of the outbreak strains highlighted an assortment of genetic determinants, stressing the need to monitor the genetic attributes of V. cholerae O1 in outbreaks for better understanding and mapping of clinical and epidemiological changes.
Keywords: Altered El Tor; India; cholera; outbreak.