Exposure assessment.

<div><p>Cholera is a diarrhoeal disease caused by <i>Vibrio cholerae</i> (<i>V</i>. <i>cholerae</i>) bacterium, with strains belonging to serogroups 01 and 0139 causing a huge proportion of the disease. <i>V</i>. <i>cholerae</i> can contaminate drinking water sources and food through poor sanitation and hygiene. This study aimed to identify environmental routes of exposure to <i>V</i>. <i>cholerae</i> within Mukuru informal settlement in Nairobi. We collected nine types of environmental samples (drinking water, flood water, open drains, surface water, shaved ice, raw produce, street food, soil, and public latrine swabs) over 12 months. All samples were analysed for <i>V</i>. <i>cholerae</i> by culture and qPCR, then qPCR-positive samples were quantified using a <i>V</i>. <i>cholerae</i> DNA standard. Data about the frequency of contact with the environment was collected using behavioural surveys. Of the 803 samples collected, 28.5% were positive for <i>V</i>. <i>cholerae</i> by qPCR. However, none were positive for <i>V</i>. <i>cholerae</i> by culture. <i>V</i>. <i>cholerae</i> genes were detected in majority of the environmental water samples (79.3%), including open drains, flood water, and surface water, but were only detected in small proportions of other sample types. Vibrio-positive environmental water samples had higher mean <i>V</i>. <i>cholerae</i> concentrations [2490–3469 genome copies (gc) per millilitre (mL)] compared to drinking water samples (25.6 gc/mL). Combined with the behavioural data, exposure assessment showed that contact with surface water had the highest contribution to the total <i>V</i>. <i>cholerae</i> exposure among children while ingestion of municipal drinking water and street food and contact with surface water made substantial contributions to the total <i>V</i>. <i>cholerae</i> exposure for adults. Detection of <i>V</i>. <i>cholerae</i> in street food and drinking water indicates possible risk of exposure to toxigenic <i>V</i>. <i>cholerae</i> in this community. Exposure to <i>V</i>. <i>cholerae</i> through multiple pathways highlights the need to improve water and sanitation infrastructure, strengthen food hygiene practices, and roll out cholera vaccination.</p></div>