Restoration of clean water supply and toilet hygiene reduces infectious diseases in post-disaster evacuation shelters: A multicenter observational study

After a massive disaster, many residents in affected areas are forced to temporarily stay in evacuation shelters. The exact impact of the state of resource supply and infrastructure in evacuation shelters on the health status of evacuees has not been sufficiently studied. Two weeks after the 2011 Great East Japan Earthquake (GEJE), comprehensive surveillance related to the health status and hygiene level was performed for all evacuation shelters (328 shelters with 46,480 evacuees at the peak) in one of the most devastating medical zones after the tsunami hit the area (Ishinomaki City). The joint relief team regularly visited all evacuation shelters across the area to assess the situation of resource supply levels, infrastructural damage, rapid need of resources, and the health status of the evacuees. In this cross-sectional observational study, we evaluated the relationship between the resource supply levels and health status among evacuees in two time periods (days 14–19 and 20–25). Among the evaluated vital resources, clean tap water supply was among the most disrupted by the disaster, and was not fully restored in most shelters during the assessment period. The cross-sectional relationship between resource supplies and morbidity was inconsistent between the two assessment periods, reflecting the multifactorial nature of health status in evacuation shelters. The clean tap water supply level at the first assessment showed a strong negative correlation with the subsequent prevalence of respiratory or gastrointestinal infectious conditions at the second assessment. Restorations in the clean tap water supply and toilet hygiene correlated each other, and both correlated with a decrease in the prevalence of gastrointestinal infectious conditions. In conclusion, disrupted clean tap water supply and inadequate toilet hygiene after a massive disaster would jointly harm the health status of those in shelters. Prompt assessments using quick visual assessment and restorations of these key resources have validity with suppressed environmental health risks among evacuees.