Tables
- TABLE 1
Main studies on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission
First author/institution [ref.] Setting Study Main findings and comments Day [1] Vo’ Euganeo, Italy RNA testing of the entire village population (3000 inhabitants) 50–75% of infected individuals were asymptomatic, representing “a formidable source” of contagion. Isolation of asymptomatic individuals was essential for controlling virus spread and epidemic seriousness. Day [2] China Screening of overseas arrivals 130 (78%) of 166 new infections identified in the 24-h period to the afternoon of Wednesday 1 April 2020 were asymptomatic. Asymptomatic infections would not be able to cause another major outbreak of COVID-19 if such individuals were kept in isolation. Zou[3] Zhuhai, Guangdong, China Monitoring SARS-CoV-2 viral loads in the upper respiratory specimens of 18 patients Higher viral loads were detected soon after symptom onset and the viral load in an asymptomatic patient was similar to that in symptomatic patients. Rothe[4] Munich, Germany Report of transmission of COVID-19 from an asymptomatic individual to four contacts The fact that asymptomatic persons are a potential source of COVID-19 infection may warrant a reassessment of the transmission dynamics of the current outbreak. WHO [5] Global Precaution recommendations The routes of COVID-19 transmission are via droplet, fomites and airborne transmission of droplet nuclei (<5 µm), with less evidence of intestine transmission. WHO continues to recommend droplet and contact precautions and not airborne precautions. Lewis [6] Global Reporting of different viewpoints Arguments in favour of and against airborne transmission and related prevention are discussed. van Doremalen [7] USA The stability of SARS-CoV-2 and SARS-CoV-1 in aerosols and on various surfaces was evaluated and their decay rates were estimated using a Bayesian regression model Aerosol and fomite transmission of SARS-CoV-2 is plausible, as the virus can remain viable and infectious in aerosols for hours and on surfaces up to days. University of Maryland [8] Global Wearing surgical masks in public could help slow COVID-19 pandemic's advance; masks may limit the spread of diseases, including influenza, rhinoviruses and coronaviruses. Migliori[9] Europe WHO consensus document The core components of infection control are discussed, together with precautions for preventing unnecessary admissions, with a focus on TB. The importance of personal protection (respirators to protect healthcare staff, other patients and visitors, and surgical masks for infectious patients) is discussed. Dharmadhikari[10] South Africa 17 MDR-TB patients wore face masks on alternate days. Ward air was exhausted to two identical chambers, each housing 90 guinea pigs breathing ward air either when patients wore surgical face masks (intervention group) or when patients did not wear masks (control group). 69 (76.6%) of 90 control guinea pigs became infected, compared with 36 (40%) of 90 intervention guinea pigs, representing a 56% (95% CI 33–70.5%) decreased risk of TB transmission when patients used masks. Surgical face masks on patients with MDR-TB significantly reduced transmission and offered an adjunct measure for reducing TB transmission from infectious patients. Leung[11] Hong Kong Quantification of the amount of respiratory virus in exhaled breath of participants with medically attended ARIs and determination of the potential efficacy of surgical face masks to prevent respiratory virus transmission 246 patients were studied. Surgical face masks significantly reduced the detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols, with a trend toward reduced detection of coronavirus RNA in respiratory droplets. The results indicate that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals. Long[12] China Systematic review and meta-analysis of the effectiveness of N95 respirators versus surgical masks to prevent influenza The use of N95 respirators compared with surgical masks is not associated with a lower risk of laboratory-confirmed influenza. It suggests that N95 respirators should not be recommended for the general public and non-high-risk medical staff (those are not in close contact with influenza patients or suspected patients). Seto[13] Hong Kong Case–control study in five hospitals 241 non-infected and 13 infected staff were surveyed regarding their use of masks, gloves and gowns, and their hand washing. 69 staff who reported the use of all four measures were not infected, while all infected staff omitted at least one measure (p=0.0224). Fewer staff who wore masks (p=0.0001), gowns (p=0.006) and washed their hands (p=0.047) were infected compared with those who did not; stepwise logistic regression was significant only for masks (p=0.011). The practice of droplet precaution and contact precaution is adequate in significantly reducing the risk of infection after exposure to patients with SARS. The protective role of masks suggests that in hospitals, infection is transmitted by droplets. CDC [14] USA Guidance to the public Core recommendations are: 1) clean your hands often; 2) avoid close contact; 3) cover your mouth and nose with a cloth when around others; 4) cover coughs and sneezes; 5) clean and disinfect. COVID-19: coronavirus disease 2019; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; WHO: World Health Organization; TB: tuberculosis; MDR-TB: multidrug-resistant TB; ARI: acute respiratory infection; CDC: Centers for Disease Control and Prevention.
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Vol 55 Issue 6
Table of Contents
Universal use of face masks for success against COVID-19: evidence and implications for prevention policies
