Shared Sanitation Facilities and Risk of COVID-19 in Resource-Poor Settings: An Agent-Based Modelling Study

Water supply and sanitation are essential household services that are frequently shared in resource-poor settings within low- and middle-income countries. Shared sanitation in particular can increase the risk of enteric pathogen transmission due to sub-optimal cleanliness of facilities used by high numbers of individuals. It also has the potential to increase the risk of respiratory disease transmission. Since sanitation is an essential need, even when stay-at-home recommendations are in place, shared sanitation may act as an important COVID-19 transmission pathway. This analysis explores how behavioral and infrastructural conditions surrounding shared sanitation may individually and interactively influence COVID-19 transmission. We developed an individual-based community transmission model parameterized from empirical literature to explore how COVID-19 transmission in shared latrines interacts with transmission at the community level. We explored COVID-19 mitigation strategies including infrastructural interventions, like increased latrine ventilation and decreased latrine sharing, and behavioral interventions, like increased handwashing and community-wide social distancing. Our review of empirical literature confirms that shared sanitation venues in resource-poor settings are relatively small with poor ventilation and high use patterns. In these contexts, we observe that shared sanitation facilities are able to act as strong drivers of respiratory disease transmission, especially when a high proportion of the population is reliant on shared facilities. Decreasing population-level dependence on shared latrines was most effective at attenuating sanitation-associated transmission, but improvements to latrine ventilation and handwashing behavior were also able to decrease transmission, especially when competing risks trade-offs via alternate transmission routes were addressed. We conclude that the type and order of interventions are important in successfully attenuating disease risk, with infrastructural and engineering controls being most effective when administered first; followed by behavioral controls after successful attenuation of sufficient alternate transmission routes. Beyond COVID-19, our modeling framework can be extended to address water, sanitation, and hygiene measures targeted at a range of environmentally mediated infectious diseases.