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

Abstract

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.

Keywords: Disaster; Evacuation shelter; Infectious diseases; Toilet hygiene; Water supply.

Figure 1

Flow diagram of enrollment for resource assessments and medical checkups. (A) Based on the information of the preliminary field survey, more than 300 evacuation shelters were inspected by the IZJRT regarding resource supply levels, infrastructural damage, and the health status of the evacuees. More than half of the shelters were mid-to-large-sized with ≥50 accommodated evacuees. A total of 28 mid-to-large-sized shelters with 9,990 evacuees were cross-sectionally assessed for the above-described modalities. (B) The timing of the resource assessments and medical checkups due to the chronological changes in the number of total shelters and accommodated evacuees in the Ishinomaki Medical Zone (total population of 220,000).

Figure 2

Geographic distribution and population size of the assessed shelters. (A) Geographic locations of the assessed 28 evacuation shelters in the Ishinomaki Medical Zone, one of the nearest cities from the epicenter of the earthquake. (B) A histogram of the population size of all public and non-public evacuation shelters established in the medical zone, confirmed by the initial visiting from day 11 to day 14. More than half of the shelters were mid-to-large-sized with the population size ≥50. (C) A histogram of the assessed 28 shelters with complete assessment data concerning the resource supply levels, infrastructural damage, and health statuses.

Figure 3

The timing of the visits, cross-sectional data, and follow-up data for each shelter. The displayed numbers aside from the shelter numbers are the reported number of accommodated evacuees in each shelter at the time of the first cross-sectional data sampling (black diamond). IZJRT, Ishinomaki Zone Joint Relief Team; GEJE, Great East Japan Earthquake.

Figure 4

Pictures of the evacuation shelters during the first assessment period. (A) A scene of a large shelter with ≥500 evacuees. This shelter was one of the most supplied and sanitized shelters with low morbidity among the evacuees. (B) A scene of a medium-sized shelter with about 100 evacuees. (C, D) Temporary emergent tap water supply facility with a water tank and six faucets. This case was assessed as “sufficient”.

Figure 5

Pictures of toilets in the shelters during and after the first assessment period. (A–E) Pictures of the actual toilet scenes during the first assessment period (days 14–19), taken by the assessment team members. Regularly cleaned and desludged temporary toilet with hand washing facility was assessed as “sufficient”. (F) A picture of the undamaged functional toilet in an evacuation shelter, taken after the second assessment period in 2011. Only the toilets of such undamaged fixed toilets were assessed as “excellent”.

Figure 6

Distributions of the assessed resource supply levels in each shelter. Each plot shows the assessed level of resource supply in each shelter. The diamonds show the medians of the distributions.

Figure 7

Prevalence of GIS by the recovery of resource supply levels. (A) The prevalence of GIS was significantly lower in shelters with improved tap water supply. (B) The prevalence of GIS was also significantly lower in shelters with improved toilet hygiene. GIS, gastrointestinal symptoms.

Figure 8

Correlation networks between resource supply levels, shelter sizes, and health status. (A) Correlation networks between resource supply levels and concurrent health statuses of the evacuees in each shelter during the first assessment period. (B) The same during the second assessment period. (C) Correlation networks between the changes (Δ) in resource supply level and in health status. (D) Correlation networks between resource supply levels during the first assessment period and delayed health statuses during the second assessment period in each shelter. GIS, gastrointestinal symptoms; URS, upper respiratory symptoms.