Disinfection of Phi6, MS2, and Escherichia coli by Natural Sunlight on Healthcare Critical Surfaces.

Ultraviolet (UV) radiation systems, commonly used to disinfect surfaces, drinking water, and air, stem from historical practice to use sunlight to disinfect household items after contagious illness. Currently, it is still recommended in viral outbreak contexts such as COVID-19, Ebola, and Marburg to expose soft surfaces to sunlight after washing with detergent or disinfecting with chlorine. However, sunlight that reaches the Earth's surface is in the UVA/UVB wavelengths, whereas UV disinfection systems typically rely on biocidal UVC. Our goal was to fill the evidence gap on the efficacy of sunlight disinfection on surface materials common in low-resource healthcare settings by seeding four surfaces (stainless steel, nitrile, tarp, cloth) with three microorganisms (viral surrogate bacteriophages Phi6 and MS2 and Escherichia coli bacteria), with and without soil load, and exposing to three sunlight conditions (full sun, partial sun, cloudy). We conducted 144 tests in triplicate and found: solar radiation averaged 737 W/m2 (SD = 333), 519 W/m2 (SD = 65), and 149 W/m2 (SD = 24) for full sun, partial sun, and cloudy conditions; significantly more surfaces averaged ≥ 4 log10 reduction value (LRV) for Phi6 than MS2 and E. coli (P < 0.001) after full sun exposure, and no samples achieved ≥ 4 LRV for partial sun or cloudy conditions. On the basis of our results, we recommend no change to current protocols of disinfecting materials first with a 0.5% chlorine solution then moving to sunlight to dry. Additional field-based research is recommended to understand sunlight disinfection efficacy against pathogenic organisms on healthcare relevant surfaces during actual outbreak contexts.

Chlorine efficacy against bacteriophage Phi6, a surrogate for enveloped human viruses, on porous and non-porous surfaces at varying temperatures and humidity.

While efficacy of chlorine against Phi6, a widely-used surrogate for pathogenic enveloped viruses, is well-documented, surfaces common to low-resource contexts are under-researched. We evaluated seven surfaces (stainless steel, plastic, nitrile, tarp, cloth, concrete, wood) and three environmental conditions-temperature (4, 25, 40 °C), relative humidity (RH) (23, 85%), and soiling-to determine Phi6 recoverability and the efficacy of disinfection with 0.5% NaOCl. Overall, Phi6 recovery was >4 log10 PFU/mL on most surfaces after drying 1 hour at all temperature/humidity conditions. After disinfection, all non-porous test conditions (48/48) achieved ≥4 LRV at 1 and 5 minutes of exposure; significantly more non-porous surfaces met ≥4 LRV than porous (p < 0.001). Comparing porous surfaces, significantly fewer wood samples met ≥4 LRV than cloth (p < 0.001); no differences were observed between concrete and either wood (p = 0.083) or cloth (p = 0.087). Lastly, no differences were observed between soil and no-soil conditions for all surfaces (p = 0.712). This study highlights infectious Phi6 is recoverable across a range of surfaces and environmental conditions, and confirms the efficacy of chlorine disinfection. We recommend treating all surfaces with suspect contamination as potentially infectious, and disinfecting with 0.5% NaOCl for the minimum contact time required for the target enveloped virus (e.g. Ebola, SARS-CoV-2).

Effectiveness of water chlorination programs along the emergency-transition-post-emergency continuum: Evaluations of bucket, in-line, and piped water chlorination programs in Cox's Bazar.

Supplying safe drinking water in humanitarian emergencies is critical, and source water chlorination is a commonly implemented intervention to provide safe water. We evaluated three different source water chlorination programs (bucket, in-line, and piped water chlorination) in the ongoing humanitarian response in Cox's Bazar refugee camps in Bangladesh. We used a mixed-methods research protocol including key informant interviews, water point observations, focus group discussions, household surveys, and water quality testing. The three evaluated programs were implemented at different response stages and required different levels of staffing, infrastructure, and community mobilization work. In the bucket chlorination program, highly contaminated open well water was chlorinated, in in-line and piped water chlorination programs, groundwater was treated. Overall, 71% of bucket, 36% of in-line, and 60% of piped water chlorination households had stored water that met free chlorine residual (FCR) criteria, respectively. Additionally, 71% of bucket, 86% of in-line, and 91% of piped water chlorination households had stored water that met Escherichia coli (E. coli) criteria (<10 E. coli CFU/100 mL). Regression results indicate presence of FCR, serving water by pouring, and higher source water pH were associated with meeting E. coli criteria. Our results highlight: no individual program fully met international standards as implemented, although each partially met standards; the importance of understanding beneficiary preferences and behavior change campaigns; and, the benefits and drawbacks of each source water chlorination program must be considered before implementation. Overall, we found appropriate source water chlorination program choice is a continuum, depending on humanitarian phase and context. Therefore, we recommend continuing context- and phase-appropriate source water chlorination programs, emphasizing consistent and acceptable chlorine dosage, implementing programmatic improvements, and incorporating user preferences to reduce microbial contamination and consequently the risk of waterborne diseases.