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

Abstract

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).

Keywords:

• Chlorine
• disinfection
• Phi6
• recovery
• surface

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article.

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

This study is made possible by the generous support of the American people through the United States Agency for International Development (USAID). The contents are the responsibility of the co-authors and do not necessarily reflect the views of USAID or the United States Government. We also thank Prof. Sylvain Moineau of the University of Laval for Phi6. We are grateful to Christine Kelly for laboratory assistance at Lancon Environmental, LLC and we thank Travis Yates and Mike Eubanks for making surface carriers.