In the U.S. Virgin Islands, 90 percent of houses rely on rainwater collected in catchment systems, such as cisterns, as the main residential water supply. During July and August 2019, the V.I. Department of Health, supported by the Centers for Disease Control and Prevention (CDC) and local partners, visited 400 households across all three islands to study the water quality of household cisterns to better understand the potential risks of waterborne illnesses.
Findings from the study will help develop improved recommendations on how to safely manage the quality of water from cisterns and help protect the health of the community.
The study identified that 80 percent of cistern water (taken directly from the cistern hatch) tested positive for E. coli contamination while 58 percent of tap water (taken from kitchen tap) sourced from cisterns tested positive for E. coli contamination. In previous studies (19 total globally) the prevalence of cisterns that have tested positive for E. coli contamination ranged from 24 percent to 92 percent, with an average of 54 percent.
Previous Department of Health studies found that 18 percent of households drink their cistern water directly.
Health officials would like to remind residents that water contaminated with E. coli should not be used for consumption, which includes drinking, cooking and brushing teeth. Furthermore, properly maintained water treatment systems, like those with multi-stage filters and/or ultraviolet (UV) light, can provide water that is safe for consumption.
During and after emergencies, cistern water may not be safe to drink. When safe water is not available, use bottled water for drinking, cooking and brushing teeth. If you do not have bottled water in an emergency situation, boil (for more than 1 minute) or disinfect your cistern water a gallon or less at a time (1/8 teaspoon of bleach for 1 gallon of water).
The Department of Health is working alongside the CDC to identify additional recommendations for households to improve cistern water quality based upon data from the study.