The primary mode of human-to-human transmission for SARS-CoV-2, the virus responsible for coronavirus disease (COVID-19), is via direct contact with an infected person and their respiratory droplets, expelled during coughing, sneezing, speaking, or breathing.1,2 These droplets can be inhaled or become deposited on surfaces such as door handles, light switches, chairs, faucets, and other frequently touched surfaces.3
Contact with contaminated surfaces (fomites) followed by touching of the eyes, mouth, or nose is another important mode of SARS-CoV-2 transmission. The relative importance of other transmission pathways are still being investigated.4,5,6 SARS-CoV-2 has been found to remain viable for several hours on surfaces such as copper (four hours) and cardboard (24 hours) and for several days on plastics and stainless steel under experimental conditions.7,8 Other studies of coronaviruses have found that viruses can remain viable for up to nine days on non-porous surfaces such as metal, glass, or plastic.9 Interventions to reduce the transmission of SARS-CoV-2 via contact routes must include frequent cleaning and disinfecting to reduce viability of the virus on potentially contaminated surfaces.10
Current guidance on the safe and appropriate use of cleaners and disinfectants in homes varies widely across Canada, and accidental exposure to dangerous disinfection by-products or improper use of bleach have been reported (personal communication with colleagues at the Drug and Poison Information Centre, British Columbia Centre for Disease Control, March 28, 2020, e-mail communication; unreferenced). This document provides information to public health professionals who may be consulted on the appropriate use of cleaning and disinfection products as well as frequency of cleaning and disinfecting in homes to protect the health of the public.
Types of Household Surfaces
Household surfaces can be categorized into food contact surfaces and environmental surfaces. Food contact surfaces are defined as surfaces that touch food or are in contact with other surfaces that touch food. Everything else is considered to be environmental surfaces, which can be further divided into high-touch and low-touch surfaces.11 Table 1 lists some common household surfaces in each of these categories. This list is not exhaustive.
Products used to reduce and inactivate microorganisms on food contact surfaces are different from those used on environmental surfaces that do not come into contact with food. This is due to the potential toxicological hazards of these products if residues contaminate foods. For food contact surfaces, the products must be approved for such use. Some products require rinsing with potable water. Manufacturer’s instructions for specific uses must be followed.
Appropriate use of cleaners, sanitizers, and disinfectants against SARS-CoV-2
SARS-CoV-2 genetic materials are enveloped by a fatty layer that is susceptible to soaps and detergents that can deactivate the virus by tearing apart its outer layer.12 It is also susceptible to other lipid solvents including hydrogen peroxide, alcohol (ethanol or isopropyl alcohol), sodium hypochlorite (bleach), benzalkonium chloride (found in most Lysol products) and peroxyacetic acid (found in surface cleaners and sanitizers) among others.9,13-18 The type of cleaner and disinfectant depends on the intent, frequency of contact, and type of surface on which they are being used. Whenever possible, use pre-mixed disinfecting cleaner products instead of mixing separate products, to avoid accidental exposure to harmful chemicals. Never mix bleach with ammonia or acid products as toxic chlorine gas and other dangerous by-products can be formed.19 Never use hot water as chlorine gas can be released when bleach is mixed with hot water.
What are cleaners, sanitizers, and disinfectants?
Cleaning involves the physical removal of dirt, debris, dust, body fluids, and other organic materials from a surface using surfactants such as detergents (soaps) or abrasive cleaners and water.20 Soil debris encompasses several categories of debris that require different types of cleaners, for example, fats, oils, and grease; proteins; carbohydrates; minerals and salts; corrosions (rust); adhesives, rubbers; and algae and fungi. Surfactants are used to disrupt fats and grease layers while caustic sodas and acid-based cleaners are used to disrupt proteins and carbohydrate layers. As debris such as dirt or organic materials may reduce the effectiveness of disinfectants, cleaners are used to pre-clean surfaces prior to sanitizers and disinfectants.16,20,21 Cleaning agents are also important to dislodge biofilm layers of microorganisms from surfaces.22 Cleaning products may kill or inactivate certain microorganisms but do not fully eliminate all of them from surfaces.21 Common cleaning products include detergents, caustic sodas, and acid-based cleaners, soaps, pre-mixed detergent products, and mops, cloths, and paper towels. Ensure cleaning products are rinsed off thoroughly with potable water before applying sanitizers/disinfectants unless otherwise indicated. Always follow the manufacturer’s instructions.
Sanitizers are defined as substances or a mixture of substances that reduce but do not necessarily eliminate microorganisms on environmental surfaces and inanimate objects. Effective sanitizers reduce microorganisms by a minimum of 99.9% or 3 log10 within 5 minutes at room temperature.23,24 On food contact surfaces, approved food-grade sanitizers can be used. Food grade sanitizers must achieve 99.999% or 5-log10 reduction of Escherichia coli and Salmonella aureus bacteria within 30 seconds at room temperature.