Herd Protection from Drinking Water, Sanitation, and Hygiene Interventions

Abstract

Herd immunity arises when a communicable disease is less able to propagate because a substantial portion of the population is immune. Nonimmunizing interventions, such as insecticide-treated bednets and deworming drugs, have shown similar herd-protective effects. Less is known about the herd protection from drinking water, sanitation, and hand hygiene (WASH) interventions. We first constructed a transmission model to illustrate mechanisms through which different WASH interventions may provide herd protection. We then conducted an extensive review of the literature to assess the validity of the model results and identify current gaps in research. The model suggests that herd protection accounts for a substantial portion of the total protection provided by WASH interventions. However, both the literature and the model suggest that sanitation interventions in particular are the most likely to provide herd protection, since they reduce environmental contamination. Many studies fail to account for these indirect effects and thus underestimate the total impact an intervention may have. Although cluster-randomized trials of WASH interventions have reported the total or overall efficacy of WASH interventions, they have not quantified the role of herd protection. Just as it does in immunization policy, understanding the role of herd protection from WASH interventions can help inform coverage targets and strategies that indirectly protect those that are unable to be reached by WASH campaigns. Toward this end, studies are needed to confirm the differential role that herd protection plays across the WASH interventions suggested by our transmission model.

Examining time‐dependent effects of water, sanitation, and hygiene (WASH) interventions using an agent‐based model

“…Diarrheal disease is transmitted through interactions between agents and the environment (Figure ). In our ABM, the transmission can be described with two pathways, which is similar to those in the model of Fuller and Eisenberg . First, infectious people shed pathogens into their household.…”

“…On the basis of Fuller and Eisenberg , we developed an agent‐based model of diarrheal disease transmission in a community using Anylogic 7.3.5, a common agent‐based simulation platform. Our ABM simulates the diarrheal disease transmission with approximately 500 individuals within 100 households.…”

“…The effects of WASH interventions on reductions in the diarrheal disease transmission have been explored through a systematic modeling approach . Despite previous studies showing that interventions have non‐trivial effects on disease incidence in a relatively long‐term period (i.e., 1‐year), our understanding of how the effects vary according to the time from implementation remains unclear.…”

Does Basic Sanitation Prevent Diarrhea? Contextualizing Recent Intervention Trials through a Historical Lens

“…One observational study from national survey data in India found that community coverage was related to diarrhea [115], but another observational study found no effect of community coverage on diarrhea in Mali [9]. Additional theoretical model analysis has suggested that all benefits from sanitation interventions come from the indirect effects due to community coverage [116]. There is not enough evidence to know if these latrine interventions could have had a stronger effect at higher coverage, but it is possible that not approaching herd protection was a factor in the observed results of the WASH-Benefits Kenya and SHINE trials.…”

Reducing Escherichia Coli Contamination on Dringking Water Stations in Pasuruan, East Java, Indonesia.

“…Fuller & Eisenberg [50] stated that understanding the role of herd protection from drinking water, sanitation, and hand hygiene (WASH) interventions can help inform coverage targets and strategies that indirectly protect those that are unable to be reached by WASH campaigns. Abalo et al [51] prominent people were invited to intermittently grace the National Sanitation Day (NSD) exercise, their invitations should be to empower the local people toesteem the importance of the programme by making it their own rather than depending on their presence to increase patronage.…”