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Shared water facilities and risk of COVID-19 in resource-poor settings: A transmission modelling study

['Michael A. L. Hayashi', 'Department Of Epidemiology', 'School Of Public Health', 'University Of Michigan', 'Ann Arbor', 'Michigan', 'United States Of America', 'Savannah Boerger', 'Kaiyue Zou', 'Sophia Simon']

Date: 2022-05

Shared water facilities are widespread in resource-poor settings within low- and middle-income countries. Since gathering water is essential, shared water sites may act as an important COVID-19 transmission pathway, despite stay-at-home recommendations. This analysis explores conditions under which shared water facility utilization may influence COVID-19 transmission. We developed two SEIR transmission models to explore COVID-19 dynamics. The first describes an urban setting, where multiple water sites are shared within a community, and the second describes a rural setting, where a single water site is shared among communities. We explored COVID-19 mitigation strategies including social distancing and adding additional water sites. Increased water site availability and social distancing independently attenuate attack rate and peak outbreak size through density reduction. In combination, these conditions result in interactive risk reductions. When water sharing intensity is high, risks are high regardless of the degree of social distancing. Even moderate reductions in water sharing can enhance the effectiveness of social distancing. In rural contexts, we observe similar but weaker effects. Enforced social distancing and density reduction at shared water sites can be an effective and relatively inexpensive mitigation effort to reduce the risk of COVID-19 transmission. Building additional water sites is more expensive but can increase the effectiveness of social distancing efforts at the water sites. As respiratory pathogen outbreaks—and potentially novel pandemics—will continue, infrastructure planning should consider the health benefits associated with respiratory transmission reduction when prioritizing investments.

Funding: MH, SB, SS, KZ, MF, and JNSE were funded by the Bill & Melinda Gates Foundation (# INV-005081). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Data Availability: Data was not collected for this modeling study. All scripts and models needed to reproduce the results presented in this manuscript are available in the following github public repository https://github.com/malhayashi/shared_water_covid .

Copyright: © 2022 Hayashi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Introduction

To control transmission of COVID-19, policies have centered around staying at home to reduce contact, supplemented by vigilant personal hygiene, mask wearing, and social distancing in shared spaces [1]. However, people living in resource-constrained contexts, specifically those living in households without access to private water, sanitation, and hygiene (WASH) facilities may be at disproportionate risk for COVID-19 transmission due to unavoidable close contact which may occur in these settings [2].

Nearly 30% of the global population relies on communal facilities of some type to fulfill their daily water needs [3]. This necessity, unyielding in the face of a pandemic, highlights the indirect impacts of resource constraints on infectious disease transmission, even when other prevention recommendations are followed. Individuals in these settings may be required to congregate at space-limited shared water sources to meet critical household needs [4,5]. Water gathering activities account for substantial amounts of time—greater than 2 hours in some rural communities [6–8]. As a result, users of communal water sites, who are often low-income, are disproportionately at risk for disease through other avenues of exposure including places of employment and through caretaking.

Due to the potential for COVID-19 transmission in public water collection sites, developing prevention and control measures is an urgent and evolving task. The Hierarchy of Controls, a framework originally developed for occupational health hazards [9], categorizes prevention strategies into those that are the most effective (but require more resources and appropriate infrastructure) and those that are less effective (but require fewer resources and therefore are more readily accessible). This hierarchy has been applied to the COVID-19 response [10,11], and funnels from highly effective elimination strategies, such as vaccination, down to the use of personal protective equipment (PPE) in the form of masks and administrative controls in the form of social distancing (Fig 1). Interventions at the bottom of the hierarchy are subject to considerable variability in behavior and adherence. Effective social distancing at water sites must take into account the functional size of the site itself and the density of users. Infrastructural changes, such as increased ventilation, lie in between vaccines and PPE. We consider increasing access to water to be higher up the Hierarchy of Controls as it is an infrastructural means of risk mitigation. While access to water is often considered in the context of reducing enteric disease risk, we argue that it may serve as a mitigation measure for COVID-19 as well by reducing the amount of social mixing and waiting that occurs at water sites.

It is important to consider the context-dependent nature of water site access and community structure when assessing the risk posed by social mixing, such as along the urban-rural continuum. Urban sites tend to have more intra-community mixing beyond shared water facilities, whereas rural inter-community mixing may be more discrete and infrequent, occurring largely through shared water sites and markets. Within the rural scope, different regions of the world have different geographic clustering norms, potentially influencing the density of users at shared water facilities. This wide variation in social structure highlights the need for context-informed decision making so that recommendations could be assessed and adapted to the local context for most effective outcomes.

COVID-19 research thus far has focused on shared WASH facilities largely in the context of hygiene and viability of SARS-CoV-2, the causative agent, on fomites. The potential impact of distinct intervention types, ranging from simple social distancing (immediate change in conditions) to an actual increase in water sites in a community (long term, resource dependent change in conditions) is unknown. The degree of exposure events to SARS-CoV-2 in a communal water site may seed outbreaks in the general community. The Pareto Principle, suggesting that around 20% of people may cause up to 80% of outbreaks [12], has been demonstrated recently for COVID-19 [13] and previously in relation to other coronaviruses [14]. In particular, this idea could be related to high risk, essential venues like shared water facilities. Although it is clear shared water sites have the potential to incur risks of COVID-19 transmission, very little is known about the relative influence of this venue.

The dearth of empirical data surrounding water facilities and COVID-19 transmission, especially in low-income settings, underscores the utility of mathematical approaches to model the potential impact of shared sites in different types of communities worldwide. The purpose of this study is to investigate how COVID-19 specifically, and respiratory infectious disease transmission broadly, may be impacted by shared water conditions in rural and urban contexts. Mathematical modeling is an important strategy used to highlight the risk incurred and explore potential mitigation strategies. To this end, we examine a range of theoretical water site scenarios. We present a deterministic, compartmental transmission model which we use to estimate the proportional impact of water-gathering contexts in COVID-19 transmission and potential reduction through water-facility-related interventions.

Our primary research question is: What are the synergistic effects of social distancing and increasing the number of water sites for COVID-19 transmission in different shared water contexts worldwide? Our secondary question is: How can we conceptualize the risk associated with shared communal water sites (i.e., public water taps) in the spread of COVID? This study seeks to provide guidance on the most effective interventions for COVID-19 transmission in different shared water contexts worldwide and recommend best practices in water infrastructure development for broad disease reduction.

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[1] Url: https://journals.plos.org/water/article?id=10.1371/journal.pwat.0000011

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