Tables
- TABLE 1
Main studies on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission
Authors Setting Study Main findings and comments Day M. BMJ 2020;368:m1165. [1] Vo’ Euganeo, Italy RNA testing of the entire village population (3000 inhabitants) 50–75% of infected individuals asymptomatic, representing “a formidable source” of contagion. Isolation of asymptomatic individuals essential for controlling virus spread and epidemic seriousness Day M. BMJ 2020; 369:m1375. [2] China Screening on overseas arrivals 130 of 166 new infections (78%) identified in the 24 h 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 L et al. N Engl J Med 2020; 382: 1177–79. [3] Zhuhai, Guangdong, China Monitoring SARS-CoV-2 viral loads in upper respiratory specimens of 18 patients Higher viral loads were detected soon after symptom onset and viral load in an asymptomatic patient was similar to that in the symptomatic patients. Rhote C. et al. N Engl J Med 2020;382:970–971. [4] Munich, Germany Report of transmission of COVID-19 from an asymptomatic individual to 4 contacts The fact that asymptomatic persons are potential sources of COVID-19 infection may warrant a reassessment of transmission dynamics of the current outbreak. World Health Organization. Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations. [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 for intestine transmission. WHO continues to recommend droplet and contact precautions and not airborne precautions. Lewis D. Is the coronavirus airborne? Experts can't agree. Nature 2020. [6] Reporting of different viewpoints Arguments in favour and against airborne transmission and related prevention are discussed. van Doremalen N. et al. N Engl J Med 2020. [7] USA Stability of SARS-CoV-2 and SARS-CoV-1 in aerosols and on various surfaces was evaluated and their decay rates estimated using a Bayesian regression model Aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days. University of Maryland. ScienceDaily, 3 April 2020. [8] USA Wearing surgical masks in public could help slow COVID-19 pandemic's advance: masks may limit the spread diseases including influenza, rhinoviruses and coronaviruses. Migliori GB, et al. Eur Respir J 2019; 53(6). [9] Europe WHO Consensus document The core components of infection control are discussed, together with precautions to prevent unnecessary admissions, with focus on tuberculosis. The importance of personal protection (respirators to protect health care staff, other patients and visitors and surgical masks for infectious patients) is discussed. Dharmadhikari AS. et al. Am J Respir Crit Care Med 2012; 185(10): 1104–1109. [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). Sixty-nine of 90 control guinea pigs (76.6%) became infected, compared with 36 of 90 intervention guinea pigs (40%) 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 offer an adjunct measure for reducing TB transmission from infectious patients. Leung NHL et al. Nature Medicine 2020. [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 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 Y. J Evid Based Med 2020. [12] China Systematic Review and meta-analysis on 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 general public and non high-risk medical staff those are not in close contact with influenza patients or suspected patients. Seto WH. Lancet 2003;361:1519–1520. [13] Hong Kong Case-control study in 5 hospitals 241 non-infected and 13 infected staff were surveyed about use of mask, gloves, gowns, and hand-washing. 69 staff reporting 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). Practice of droplets precaution and contact precaution is adequate in significantly reducing the risk of infection after exposures to patients with SARS. The protective role of masks suggests that in hospitals, infection is transmitted by droplets. Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19). How to Protect Yourself & Others. [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 cover when around others; 4. Cover cough and sneezes; 5. Clean and disinfect.
Vol 56 Issue 4
Table of Contents
Universal use of face masks for success against COVID-19: evidence and implications for prevention policies
