When a new pathogen emerges, it takes time to get the organism in the hands of researchers who can safely handle and study its behavior in a controlled manner. Typically, the Centers for Disease Control and Prevention (CDC) or the National Institute of Allergy and Infectious Diseases (NIAID) catalogs the organism and prepares it for dissemination to a specific set of scientists. In the case of SARS-CoV-2, the virus was handled by the Biodefense and Emerging Infections Research Resources Repository (BEI Resources), which is managed by the NIAID .
In the absence of direct testing data, the EPA’s Emerging Pathogen program takes effect. Disinfectants that had been proven effective against similar viruses could be registered and added to the EPA’s List N  These products were deemed likely to work against SARS-CoV-2 because they inactivate a harder-to-kill virus or another human coronavirus . While this list served as a practical and necessary guide during the initial months, it relied on scientific assumptions and not hard data. Research was still needed to show how each disinfectant reacts when it encounters SARS-CoV-2 for them to be deemed effective.
Unlike bacteria, viruses require a host cell in order to infect and replicate. While related coronaviruses have proven difficult to grow in the lab, SARS-CoV-2 adapted to cell culture quickly. In the U.S., the virus became available for research in March to a select number of Biosafety Level 3 containment laboratories that have proof of eligibility from the CDC or the United States Department of Agriculture (USDA) .
To demonstrate the efficacy of a disinfectant, companies need to follow the guidance of the EPA – specifically, OCSPP 810.2200 - Disinfectants for Use on Environmental Surfaces: Guidance for Efficacy Testing. Viral testing is supported using an ASTM International standard test method, ASTM E1053 ‘Test Method for Efficacy of Viricidal Agents Intended for Inanimate Environmental Surfaces.’ 
To perform the testing, the SARS-CoV-2 virus is grown in cell culture until a sufficient number is reached (typically more than 63,000 viable viral particles). Soil, in the form of animal serum, is added to the virus ‘stock’ in order to replicate the environmental conditions the virus favors. Soil is known to deactivate certain disinfectants, which creates an additional challenge. The mixture of virus and soil is then applied to the bottom of a glass petri dish and allowed to dry. This again simulates how the virus may be found in the environment. Disinfectants are applied to the dried virus in a manner that mimics a real-world situation. In the case of disinfectant wipes, they are folded and wiped across the surface in a controlled manner. Following the contact time, which can vary based on the wipe, the virus is scraped from the bottom of the petri dish and collected for regrowth in cell culture. Studies have shown the incubation time for SAR-CoV-2 is approximately seven days under specific temperature and atmospheric conditions.
Unlike bacteria, viruses cannot be seen by the naked eye or even under high microscopy. Instead, scientists use a microscope to look for the infectivity of the virus upon its host cell – the cytopathic effect. Using the resulting microscopy, a reduction from the initial population can be determined. The EPA requires a 99.9% reduction to prove effectiveness .
Status of PDI Hospital Grade Disinfectant Wipes
PDI began testing on its first product, Super Sani-Cloth wipes, in April. Super Sani-Cloth wipes are a hospital-grade disinfectant wipe, which have been proven effective against three viruses that are harder to kill than SARS-CoV-2—rhinovirus, adenovirus and rotavirus—thereby qualifying the product for EPA’s List N: Disinfectants for Use Against SARS-CoV-2 (COVID-19). The active ingredients in Super Sani-Cloth wipes are a mixture of quaternary ammonium compounds and isopropanol.
Testing on the Super Sani-Cloth wipes was performed by Microbac Laboratories, Inc., an independent laboratory that performs environmental, food, and life science testing. Microbac has been at the forefront of testing for many emerging pathogens, such as Influenza H1N1 (2009), SARS, and MERS. They were one of the first laboratories to test directly against SARS-CoV-2, drawing on both their knowledge of pathogenic viruses and EPA testing expertise. They performed testing using the protocol described above.
Microbac’s results showed that Super Sani-Cloth wipes achieved a three-log reduction (99.9%) against the virus, in compliance with the EPA’s OCSPP 810.2200 — Disinfectants for Use on Environmental Surfaces: Guidance for Efficacy Testing.
After receiving positive data from Microbac in June, the data were submitted to the EPA in early July. If approved by the EPA, Super Sani-Cloth wipes will receive label approval that the product has been tested as effective against the virus. Testing of additional PDI products on EPA’s List N is underway.
While we may assume that SARS-CoV-2 is easy to disinfect because it is an enveloped virus, we cannot guarantee efficacy until it is tested directly against the specific strain of the virus. We want to arm our healthcare professionals and community with disinfectants that we know work against SARS-CoV-2, with specific protocols and robust science.
1. Rutala, W.A and Weber, D.J (March, 2020) Focus on Surface Disinfection When Fighting COVID-19, Infection Control Today
3. Environmental Protection Agency (August, 2020), List N: Disinfectants for Use Against SARS-CoV-2 (COVID-19). Retrieved from https://www.epa.gov/pesticide-registration/list-n-disinfectants-use-against-sars-cov-2-covid-19
4. Environmental Protection Agency (August, 2016) GUIDANCE TO REGISTRANTS: PROCESS FOR MAKING CLAIMS AGAINST EMERGING VIRAL PATHOGENS NOT ON EPA-REGISTERED DISINFECTANT LABELS. Retrieved from https://www.epa.gov/sites/production/files/2016-09/documents/emerging_viral_pathogen_program_guidance_final_8_19_16_001_0.pdf
6. Environmental Protection Agency (August, 2019), Product Performance Test Guideline, OCSPP 810.2200, Disinfectants for Use on Environmental Surfaces, Guidance for Efficacy Testing https://www.regulations.gov/document?D=EPA-HQ-OPPT-2009-0150-0036