Integrated epidemiological investigation of the 2024 cholera outbreak in Sulaymaniyah Governorate- Iraq

AIMS: Cholera outbreaks continue intermittently in Iraq. Recent outbreaks have highlighted the need for investigations. This study aimed to conduct an integrated epidemiological investigation of a cholera outbreak in Iraq using microbiological, molecular, immunological, and environmental approaches. METHODS: This descriptive epidemiological study investigated the surveillance of acute watery diarrhoea (AWD) and environmental screening for Vibrio cholerae in 2024-2025. The microbiological and molecular characterisations, including virulence profiling, antimicrobial susceptibility, multilocus sequence typing (MLST), and herd immunity, were explored. RESULTS: A total of 136 cholera cases were identified in 2024, corresponding to an attack rate of 6.0 per 100 000 population. The outbreak was moderate in size, temporally restricted to August-November period, urban-centred, and affected both sexes of adults. All clinical isolates were toxigenic Vibrio cholerae O1 El Tor Ogawa and belonged to the distributed pandemic sequence type (ST) 69. Environmental detection was rare (2/103, 1.9%) and confined to non-toxigenic, genetically distinct isolates of sequence type (ST) 1994. Multidrug resistance was detected in 77.4% of clinical isolates, which predominantly exhibited moderate biofilm formation and were eliminated at low chlorine concentration (2 mg l⁻¹), whereas environmental isolates exhibited stronger biofilm formation and higher chlorine tolerance. Serological analysis indicated low population immunity (2.2%). No cholera cases were recorded in 2025. CONCLUSIONS: This cholera outbreak was moderate in size and showed predominantly human-mediated transmission in a low-immunity urban population. The clinical isolates were Vibrio cholerae ST69 and exhibited antibacterial resistance and biofilm production. These findings provided insights for early detection and control of future outbreaks.