Table 2.

Mechanistic evidence and effectiveness of common non-pharmaceutical interventions

Non-pharmaceutical intervention		Targeted mode of transmissiona	Mechanism of action	Mechanistic evidenceb	Effectivenessc
PPE and hygiene practice	Hand hygiene	Contact	Soaps remove organic substances by detergent properties Alcohol denatures proteins in the presence of water	Alcohol had higher viricidal activity on enveloped viruses than on non-enveloped viruses Alcohol-based hand sanitizers are more efficacious than soaps with regard to pathogen inactivation in vivo	Multiple systematic reviews suggested hand hygiene alone is significantly associated with reduced respiratory illness but not influenza virus infection in community settings Studies on the effectiveness of hand hygiene in reducing respiratory virus transmission in health-care settings were not identified Insufficient studies to compare the efficacies of soaps versus alcohol-based hand sanitizers against respiratory infections
	Face coverings	Droplet and aerosol (contact)	As source control: when worn by an infected individual, reduce virus release to the environment by filtration and immediate virus exposure of nearby healthy individuals by deflection As protection: when worn by a healthy individual, reduce exposure to virus-laden droplets and aerosols in the air Might also reduce contact transmission by reducing the frequency of hands touching respiratory mucosa	As source control: surgical masks efficaciously reduced influenza virus and coronavirus release from infected individuals by filtration (efficacies on exhaled droplets and aerosols may differ between viruses) Studies using mannequins suggested deflection is also important in reducing virus release As protection against close-range transmission: cloth masks, surgical masks and respirators were efficacious against artificial bacteriophage or influenza virus aerosol challenge by filtration As protection against long-range transmission: in the absence of environmental airflow only 1% of radiolabeled saline aerosols generated from the source mannequin reached the exposed mannequin 3 feet apart, where only fitted respirators but not surgical masks reduced exposure to aerosols	Multiple systematic reviews of observational studies or randomized trials mostly suggested the use of face coverings alone, or in combination with other non-pharmaceutical interventions, is effective in reducing the risk of respiratory illness or respiratory virus transmission in health-care and high-risk community settings Low adherence to use of a face shield during high-risk procedures associated with higher risk of respiratory illnesses in health-care workers Preliminary evidence suggested face mask use by household members before the person with the primary case developed symptoms is significantly associated with reduced SARS-CoV-2 household transmission
Environmental disinfection and dilution	Surface cleaning	Contact (droplet and aerosol)	Common disinfectants in health-care settings: 0.1 M sodium hydroxide, 70% ethanol, 70% 1-propanol, ethylene oxide and sodium hypochlorite Common household cleaning agents: liquid soap, 1% bleach and antimicrobial or antiviral wipes Both disinfect contaminated surfaces by virus inactivation Might also reduce droplet or aerosol transmission by reducing fomites available for resuspension	Common disinfectants in health-care settings effectively inactivated influenza virus and coronaviruses on surfaces in experimental settings Common household cleaning agents effectively inactivated (enveloped) influenza virus, but were less effective for (non-enveloped) adenovirus in experimental settings Biweekly disinfection of toys significantly reduced the presence of virus genetic material in the environment for adenovirus, rhinovirus and RSV, but not coronaviruses, parainfluenza virus and bocavirus, in nurseries in a randomized trial	A systematic review found limited epidemiological studies on the effectiveness of surface and object cleaning in reducing community respiratory virus transmission during pandemics Biweekly disinfection of toys did not reduce respiratory illness in nurseries in a randomized trial The combined use of an alcohol-based hand sanitizer and chloride wipes, compared with hand washing, did not reduce respiratory illness in elementary school students in a randomized trial. Daily household cleaning was significantly associated with reduced household transmission of SARS-CoV-2
	Air dilution by ventilation and directional airflow	Droplet and aerosol	Ventilation is the intentional introduction of outdoor air into a building by mechanical ventilation (for example, fans, ductwork or air conditioning) or natural ventilation (for example, windows) Directional airflow provides clean air from the cleanest area to less clean areas	Lower ventilation associated with rhinovirus RNA detection in the air in an office environment in an observational study	Multiple systematic reviews suggested strong and sufficient evidence supporting the association between indoor ventilation and airflow patterns with transmission of SARS-CoV, influenza virus, measles virus and varicella zoster virus Directional airflow may reduce the risk of airborne infection in vulnerable individuals or transmission in health-care and community settings
	Air and surface disinfection by UVGI	Aerosol and contact	Use of UV light in the germicidal range (200–320 nm), especially UV-C (200–280 nm), to crosslink nucleic acids Air disinfection: in upper-room UVGI, irradiation is confined to the area above the occupants’ heads to minimize direct exposure, but requires good vertical air movement in the room; in in-duct UVGI, air passes through ventilation systems and is irradiated inside before recirculation or exhaustion Surface disinfection: UVGI is used on internal surfaces of ventilation systems, or surfaces and equipment	UV-C efficiently inactivated experimentally generated aerosols containing influenza virus or coronaviruses, but was less effective for adenovirus At higher relative humidity, increased susceptibility to UV-C was observed for experimentally generated aerosols containing adenovirus, but decreased susceptibility to UV-C was observed for influenza virus and vaccinia virus UV-C efficiently inactivated experimentally generated MERS-CoV on glass slides Upper-room UVGI efficiently reduced infectious vaccina virus aerosols in a simulated hospital room UVGI significantly inactivated experimentally inoculated influenza virus on respirators	Upper-room UVGI was shown to prevent airborne transmission of measles virus in schools Upper-room UVGI was associated with reduced influenza virus infections among individuals with tuberculosis Randomized trials evaluating the effectiveness of UVGI for air or surface disinfection in reducing respiratory virus transmission were not identified.

See Supplementary Table 2 for supporting references. MERS-CoV, Middle East respiratory syndrome-related coronavirus; PPE, personal protective equipment; RSV, respiratory syntactical virus; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; UV, ultraviolet; UVGI, ultraviolet germicidal irradiation. ^aThe mode or modes of transmission listed in parentheses indicate possible but presumably less important transmission via that mode. ^bMechanistic evidence with regard to virus reduction or inactivation. ^cEffectiveness with regard to prevention of respiratory illness or respiratory virus transmission.