Epidemiologic study of Vibrio cholerae O1 and O139 in Thailand: At the advancing edge of the eighth pandemic

Vibrio cholerae O139 Bengal emerged on the Indian subcontinent in late 1992 and was first recognized in Thailand in 1993. To characterize the epidemiology of this disease, a hospital-based case-control study was conducted in Samutsakom, a port city 30 km southwest of Bangkok, Between November 15, 1993, and June 3, 1994, 366 patients were confirmed to have cholera by culture, including 165 (45%) with O139 Bengal, 191 (52%) with O1 Ogawa, and 10 (3%) with both serogroups, During the same time period the previous year, 319 culture-confirmed cholera cases occurred, all serogroup O1. Questionnaires were obtained from 105 patients with O139 Bengal and 103 with O1 infections; for each case patient, two asymptomatic age- and sex-matched control persons were selected, Of the patients with O139 Bengal infections, 93% were adults (greater than or equal to 15 years) compared with 92% of patients with O1 infections, Risk factors for cholera identified by case-control comparisons were similar for the two serogroups and included consumption of untreated water, uncooked seafood, and food served at group gatherings, V. cholerae O139 Bengal has emerged in Thailand as a cause of endemic cholera, with epidemiologic features and incidence similar to those of the preexisting O1 strain.