Update with consideration of Omicron – Interim COVID-19 infection prevention and control in the health care setting when COVID-19 is suspected or confirmed– December 23, 2021

With the identification of the new COVID-19 variant of concern-Omicron, this update has been developed to emphasize and provide additional recommendations to the COVID-19 infection prevention and control measures outlined in the COVID-19 infection prevention and control guidance documents. These recommendations are for all health care settings (acute care, long term care, home care and ambulatory/outpatient care).


On November 26, 2021, WHO designated the variant B.1.1.529 (Omicron variant) a variant of concern (VOC). Subsequently, on November 28, 2021, the Canadian SARS-CoV-2 Variant Surveillance Group designated it as a Variant of Concern for Canada. Omicron is a highly divergent variant with a high number of mutations, many of these found on the spike protein. The Omicron variant has been shown to be much more transmissible than the Delta variant and has some vaccine immune escape. It is unknown if the disease severity will be different than other circulating variants.

Factors affecting the risk of acquisition of healthcare associated SARS-CoV-2 infection include:

Evidence on the transmission of SARS-CoV-2 virus has advanced rapidly and continues to emerge. Respiratory fluids continue to be the primary mode of transmission for COVID-19 via large respiratory droplets and small aerosol particles. Infections occur when respiratory mucosa (mouth, nose, eyes) are exposed to these respiratory droplets and aerosol particles. Individuals can release SARS-CoV-2 virus particles during any exhalations (e.g., talking, breathing, singing, exercising, coughing, sneezing). These aerosol particles can remain suspended in the air, and be inhaled into the respiratory tract of another person. With the arrival of the very transmissible Omicron variant, that appears to have some degree of immune escape, this new information is considered in these interim recommendations for infection prevention and control in health care settings.


Recommendations for health care settings include the following:

Aerosol exposure – Historically, certain procedures were thought to pose a higher risk for health care workers on the basis of case–control studies, mainly from SARS-CoV-1, that reported associations between selected procedures and health care worker infections. These have been called Aerosol Generating Medical Procedures (AGMPs). As scientific inquiry quantifies the aerosols produced by such procedures, it appears that they do not cause any more aerosols than coughing, singing or talking loudly. Aerosol production can also vary by individual. As these concepts are studied, a better understanding may lead to a change in infection control guidance. Until then it is prudent to continue to use fit tested N95 respirators, eye protection, gowns and gloves for all AGMPs.

Health care workers can choose to wear a respirator at any time taking into account such factors as the community incidence of SARS-CoV-2, patient’s ability to tolerate a mask, patient behaviours such as shouting or heavy breathing, requirement of extensive or prolonged close proximity, and other factors.

Masking for the full duration of shifts or visits

Given ongoing community spread of COVID-19 within Canada and evidence that transmission occurs from those who have few or no symptoms, masking for the full duration of shifts or visits has become normal practice during the COVID-19 pandemic. The rationale for full-shift or visit masking of all staff and visitors is to reduce the risk of transmitting COVID-19 from staff or visitors to others, at a time when no symptoms of illness are recognized, but the virus can be transmitted. The mask also protects the wearer. Depending on community transmission rates, the mask chosen can be a medical mask or a respirator. There is increasing evidence that the fit of the mask is the most important feature. Visitors should wear well-fitting medical masks or KN95 respirators (recognizing that there are many counterfeit KN95 respirators that may be difficult to verify at point of entry).

Employers must ensure that:

For all other COVID-19 infection prevention and control guidance measures please see: COVID-19 infection prevention and control guidance documents by healthcare sector.


Footnote 1

Adenaiye OO, Lai J, de Mesquita PJB, et al; University of Maryland StopCOVID Research Group. Infectious SARS-CoV-2 in exhaled aerosols and efficacy of masks during early mild infection. Clin Infect Dis. 2021. [PMID: 34519774] doi:10.1093/cid/ciab797

Return to footnote 1 referrer

Footnote 2

Alsved M, Matamis A, Bohlin R, et al. Exhaled respiratory particles during singing and talking. Aerosol Science and Technology. 2020;54(11):1245-1248. doi:10.1080/02786826.2020.1812502

Return to footnote 2 referrer

Footnote 3

Asadi S, Wexler AS, Cappa CD, Barreda S, Bouvier NM, Ristenpart WD. Aerosol emission and superemission during human speech increase with voice loudness. Sci Rep. Feb 20 2019;9(1):2348. doi:10.1038/s41598-019-38808-z

Return to footnote 3 referrer

Footnote 4

Asadi S, Wexler AS, Cappa CD, Barreda S, Bouvier NM, Ristenpart WD. Effect of voicing and articulation manner on aerosol particle emission during human speech. PLoS One. 2020;15(1):e0227699. doi:10.1371/journal.pone.0227699

Return to footnote 4 referrer

Footnote 5

Bourouiba L. Turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of COVID-19. JAMA.2020;323:1837-1838. [PMID: 32215590] doi:10.1001/jama.2020.4756

Return to footnote 5 referrer

Footnote 6

Brooks JT, Beezhold DH, Noti JD, et al. Maximizing fit for cloth and medical procedure masks to improve performance and reduce SARS-CoV-2 transmission and exposure, 2021. MMWR Morb Mortal Wkly Rep. 2021;70:254-257. [PMID: 33600386] doi:10.15585 /mmwr.mm7007e1

Return to footnote 6 referrer

Footnote 7

Brown J, Gregson FKA, Shrimpton A, et al. A quantitative evaluation of aerosol generation during tracheal intubation and extubation. Anaesthesia. 2021;76:174-181. [PMID: 33022093] doi:10.1111/anae.15292

Return to footnote 7 referrer

Footnote 8

Buonanno G, Stabile L, Morawska L. Estimation of airborne viral emission: Quanta emission rate of SARS-CoV-2 for infection risk assessment. Environment international. May 11 2020;141:105794.

Return to footnote 8 referrer

Footnote 9

Chan P-C, Fang C-T. The role of ventilation in tuberculosis control. J Formos Med Assoc 2021;120(6):1293-1295

Return to footnote 9 referrer

Footnote 10

Chan VW , Ng HH , Rahman L , et al. Transmission of severe acute respiratory syndrome coronavirus 1 and severe acute respiratory syndrome coronavirus 2 during aerosol-generating procedures in critical care: a systematic review and meta-analysis of observational studies. Crit Care Med. 2021;49:1159-1168. [PMID: 33749225] doi:10.1097/CCM.0000000000004965

Return to footnote 10 referrer

Footnote 11

Chen W, Zhang N, Wei J, et al. Short-range airborne route dominates exposure of respiratory infection during close contact. Build Environ. 2020;176:106859. doi:10.1016/j.buildenv.2020.106859

Return to footnote 11 referrer

Footnote 12

Chen WQ, Ling WH, Lu CY, Hao YT, Lin ZN, et al. Which preventive measures might protect health care workers from SARS? BMC Public Health 9:81. 2009;1

Return to footnote 12 referrer

Footnote 13

Cheng VC, Fung KS, Siu GK, et al. Nosocomial outbreak of coronavirus disease 2019 by possible airborne transmission leading to a superspreading event. Clin Infect Dis. 2021;73:e1356-e1364. [PMID: 33851214] doi:10.1093/cid/ciab313

Return to footnote 13 referrer

Footnote 14

Coleman KK, Tay DJW, Sen Tan K, et al. Viral load of SARS-CoV-2 in respiratory aerosols emitted by COVID-19 patients while breathing, talking, and singing. Clin Infect Dis. 2021. [PMID: 34358292]doi:10.1093/cid/ciab691

Return to footnote 14 referrer

Footnote 15

Crawford C, Vanoli E, Decorde B, et al. Modeling of aerosol transmission of airborne pathogens in ICU rooms of COVID-19 patients with acute respiratory failure. Sci Rep 2021;11:11778

Return to footnote 15 referrer

Footnote 16

Doung-Ngern P, Suphanchaimat R, Panjangampatthana A, et al. Case-control study of use of personal protective measures and risk for SARS-CoV 2 infection, Thailand. Emerg Infect Dis. 2020;26:2607-2616. [PMID: 32931726] doi:10.3201/eid2611.203003

Return to footnote 16 referrer

Footnote 17

Echternach M, Gantner S, Peters G, et al. Impulse Dispersion of Aerosols during Singing and Speaking: A Potential COVID-19 Transmission Pathway. Am J Respir Crit Care Med. Dec 1 2020;202(11):1584-1587. doi:10.1164/rccm.202009-3438LE

Return to footnote 17 referrer

Footnote 18

Edwards DA, Ausiello D, Salzman J, et al. Exhaled aerosol increases with COVID-19 infection, age, and obesity. Proc Natl Acad Sci U S A. Feb 23 2021;118(8)doi:10.1073/pnas.2021830118

Return to footnote 18 referrer

Footnote 19

Enhancing Readiness for Omicron (B.1.1.529): Technical Brief and Priority Actions for Member States - 28 November 2021. UK Health Security Agency. SARS-CoV-2 variants of concern and variants under investigation in England: technical briefing 29 [Internet]. London: Crown Copyright; 2021 [cited 2021 Dec 10].

Return to footnote 19 referrer

Footnote 20

European Centre for Disease Prevention and Control. Threat Assessment Brief: Implications of the emergence and spread of the SARS-CoV-2 B.1.1. 529 variant of concern (Omicron) for the EU/EEA. https://www.ecdc.europa.eu/en/publications-data/threat-assessment-brief-emergence-sars-cov-2- variant- b.1.1.529 4

Return to footnote 20 referrer

Footnote 21

Fennelly KP. Particle sizes of infectious aerosols: Implications for infection control. Lancet Respir Med 2020;8(9):914-924

Return to footnote 21 referrer

Footnote 22

Goldberg L, Levinsky Y, Marcus N, et al. SARS-CoV-2 infection among health care workers despite the use of surgical masks and physical distancing—the role of airborne transmission. Open Forum Infect Dis. 2021;8:ofab036. [PMID: 33732749] doi:10.1093/ofid /ofab036

Return to footnote 22 referrer

Footnote 23

Gaeckle NT, Lee J, Park Y, et al. Aerosol generation from the respiratory tract with various modes of oxygen delivery. Am J Respir Crit Care Med. 2020;202:1115-1124. [PMID: 32822208] doi:10.1164/rccm.202006-2309OC

Return to footnote 23 referrer

Footnote 24

Greenhalgh T, Jimenez JL, Prather KA, et al. Ten scientific reasons in support of airborne transmission of SARS-CoV-2. Lancet. 2021;397:1603- 1605. [PMID: 33865497] doi:10.1016/S0140-6736(21)00869-2

Return to footnote 24 referrer

Footnote 25

Grijalva CG, Rolfes MA, Zhu Y, et al. Transmission of SARSCOV-2 infections in households - Tennessee and Wisconsin, April-September 2020. MMWR Morb Mortal Wkly Rep. 2020;69:1631-1634. [PMID: 33151916] doi:10.15585/mmwr.mm6944e1

Return to footnote 25 referrer

Footnote 26

Hamner L, Dubbel P, Capron I, et al. High SARS-CoV-2 attack rate following exposure at a choir practice - Skagit County, Washington, March 2020. MMWR Morb Mortal Wkly Rep. 2020;69:606-610. [PMID: 32407303] doi:10.15585/mmwr.mm6919e6

Return to footnote 26 referrer

Footnote 27

Hu M, Lin H, Wang J, et al. Risk of coronavirus disease 2019 transmission in train passengers: an epidemiological and modeling study. Clin Infect Dis. 2021;72:604-610. [PMID: 32726405] doi:10.1093/cid /ciaa1057

Return to footnote 27 referrer

Footnote 28

Jacob JT, Baker JM, Fridkin SK, et al. Risk factors associated with SARS-CoV-2 seropositivity among US health care personnel. JAMA Netw Open. 2021;4:e211283. [PMID: 33688967] doi:10.1001/jamanetworkopen.2021.1283

Return to footnote 28 referrer

Footnote 29

Shah ASV, Wood R, Gribben C, et al. Risk of hospital admission with coronavirus disease 2019 in healthcare workers and their households: nationwide linkage cohort study. BMJ. 2020;371: m3582. [PMID: 33115726] doi:10.1136/bmj.m3582

Return to footnote 29 referrer

Footnote 30

Johansson MA, Quandelacy TM, Kada S, et al. SARS-CoV-2 transmission from people without COVID-19 symptoms. JAMA Netw Open. 2021;4:e2035057. [PMID: 33410879] doi:10.1001/jamanetworkopen.2020.35057

Return to footnote 30 referrer

Footnote 31

Karan A, Klompas M, Tucker R, et al; CDC Prevention Epicenters Program. The risk of SARS-CoV-2 transmission from patients with undiagnosed Covid-19 to roommates in a large academic medical center. Clin Infect Dis. 2021. [PMID: 34145449] doi:10.1093/cid/ciab564

Return to footnote 31 referrer

Footnote 32

Kawasuji H, Takegoshi Y, Kaneda M, et al. Transmissibility of COVID-19 depends on the viral load around onset in adult and symptomatic patients. PLoS One. 2020;15:e0243597. [PMID: 33296437] doi:10.1371/journal.pone.0243597

Return to footnote 32 referrer

Footnote 33

Klompas M, Baker M, Rhee C. What is an aerosol-generating procedure. JAMA Surg. 2021;156:113-114. [PMID: 33320188] doi:10.1001/jamasurg.2020.6643

Return to footnote 33 referrer

Footnote 34

Klompas M, Baker MA, Rhee C, et al. A SARS-CoV-2 cluster in an acute care hospital. Ann Intern Med. 2021;174:794-802. [PMID: 33556277] doi:10.7326/M20-7567

Return to footnote 34 referrer

Footnote 35

Klompas M, Baker MA, Griesbach D, et al. Transmission of SARS-CoV-2 from asymptomatic and presymptomatic individuals in healthcare settings despite medical masks and eye protection. Clin Infect Dis. 2021. [PMID: 33704451] doi:10.1093/cid/ciab218

Return to footnote 35 referrer

Footnote 36

Klompas M, Ye S, Vaidya V, et al. Association between airborne infection isolation room utilization rates and healthcare worker COVID-19 infections in two academic hospitals. Clin Infect Dis. 2021. [PMID: 34599821] doi:10.1093/cid/ciab849

Return to footnote 36 referrer

Footnote 37

Lam-Hine T, McCurdy SA, Santora L, et al. Outbreak associated with SARS-CoV-2 B.1.617.2 (Delta) variant in an elementary school -Marin County, California, May-June 2021. MMWR Morb Mortal Wkly Rep. 2021;70:1214-1219. [PMID: 34473683] doi:10.15585/mmwr.mm7035e2

Return to footnote 37 referrer

Footnote 38

Lee LYW, Rozmanowski S, Pang M, et al. SARS-CoV-2 infectivity by viral load, S gene variants and demographic factors and the utility of lateral flow devices to prevent transmission. Clin Infect Dis.2021. [PMID: 33972994] doi:10.1093/cid/ciab421

Return to footnote 38 referrer

Footnote 39

Leung NHL. Transmissibility and transmission of respiratory viruses. Nat Rev Microbiol 2021;19:528-545.

Return to footnote 39 referrer

Footnote 40

Leung NHL, Xu C, Ip DK, et al. Review article: the fraction of influenza virus infections that are asymptomatic: a systematic review and meta-analysis. Epidemiology. 2015;26:862-72. [PMID: 26133025] doi:10.1097/EDE.0000000000000340

Return to footnote 40 referrer

Footnote 41

Leung NHL, Chu DKW, Shiu EYC, et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med. 2020;26:676-680. [PMID: 32371934] doi:10.1038/s41591-020-0843-2

Return to footnote 41 referrer

Footnote 42

Li Y, Qian H, Hang J, et al. Probable airborne transmission of SARSCoV-2 in a poorly ventilated restaurant. Build Environ. 2021;196:107788. [PMID: 33746341] doi:10.1016/j.buildenv.2021.107788

Return to footnote 42 referrer

Footnote 43

Lindsley WG, Derk RC, Coyle JP, et al. Efficacy of portable air cleaners and masking for reducing indoor exposure to simulated exhaled SARSCoV-2 aerosols - United States, 2021. MMWR Morb Mortal Wkly Rep.2021;70:972-976. [PMID: 34237047] doi:10.15585/mmwr.mm7027e1

Return to footnote 43 referrer

Footnote 44

Liu W, Tang F, Fang L-Q, De Vlas SJ, Ma H-J, et al. Risk factors for SARS infection among hospital healthcare workers in Beijing: A case control study. Trop Med Int Health. 2009;14:52–59

Return to footnote 44 referrer

Footnote 45

Loeb M, McGeer A, Henry B, Ofner M, Rose D, et al. SARS among critical care nurses, Toronto. Emerg Infect Dis. 2004;10:251–255

Return to footnote 45 referrer

Footnote 46

Lordon RG, Roberts RM. Droplet expulsion from the respiratory tract. Am Rev Respir Dis 1967;95(3):435-442.

Return to footnote 46 referrer

Footnote 47

Lu J, Gu J, Li K, et al. COVID-19 outbreak associated with air conditioning in restaurant, Guangzhou, China, 2020. Emerg Infect Dis. 2020;26:1628-1631. [PMID: 32240078] doi:10.3201/eid2607.200764

Return to footnote 47 referrer

Footnote 48

Ma HJ, Wang HW, Fang LQ, Jiang JF, Wei MT, et al. A case-control study on the risk factors of severe acute respiratory syndromes among health care workers. Chung-Hua Liu Hsing Ping Hsueh Tsa Chih Chinese Journal of Epidemiology. 2004;25:741–744

Return to footnote 48 referrer

Footnote 49

Marks M, Millat-Martinez P, Ouchi D, et al. Transmission of COVID-19 in 282 clusters in Catalonia, Spain: a cohort study. Lancet Infect Dis. 2021;21:629-636. [PMID: 33545090] doi:10.1016/S1473-3099(20)30985-3

Return to footnote 49 referrer

Footnote 50

McEllistrem MC, Clancy CJ, Buehrle DJ, et al. SARS-CoV-2 is associated with high viral loads in asymptomatic and recently symptomatic healthcare workers. PLoS One. 2021;16:e0248347. [PMID: 33735264] doi:10.1371/journal.pone.0248347

Return to footnote 50 referrer

Footnote 51

Miller SL, Nazaroff WW, Jimenez JL, et al. Transmission of SARS-CoV-2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event. Indoor Air. 2021;31:314-323. [PMID: 32979298] doi:10.1111/ina.12751

Return to footnote 51 referrer

Footnote 52

Mo Y, Eyre DW, Lumley SF, et al. Transmission dynamics of SARS-CoV-2 in the hospital setting. medRxiv. Preprint posted online 1 May 2021. doi:10.1101/2021.04.28.21256245

Return to footnote 52 referrer

Footnote 53

O’Kelly E, Arora A, Pirog S, Ward J, Clarkson PJ (2021) Comparing the fit of N95, KN95, surgical, and cloth face masks and assessing the accuracy of fit checking. PLoS ONE 16(1): e0245688

Return to footnote 53 referrer

Footnote 54

Morawska L., Johnson GR, Ristovski ZD, et al. Size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities. Aerosol Sci. 2009;40(3):256-269

Return to footnote 54 referrer

Footnote 55

Nardell EA, Nathavitharana RR. Airborne spread of SARS-CoV-2 and a potential role for air disinfection. JAMA. 2020;324:141-142. [PMID: 32478797] doi:10.1001/jama.2020.7603

Return to footnote 55 referrer

Footnote 56

Oksanen LAH, Sanmark E, Oksanen SA, et al. Sources of healthcare workers' COVID-19 infections and related safety guidelines. Int J Occup Med Environ Health. 2021;34:239-249. [PMID: 33847307] doi:10.13075/ijomeh.1896.01741

Return to footnote 56 referrer

Footnote 57

O’Neil CA, Li J, Leavey A, et al; Centers for Disease Control and Prevention Epicenters Program. Characterization of aerosols generated during patient care activities. Clin Infect Dis. 2017;65:1335-1341. [PMID: 29017249] doi:10.1093/cid/cix535

Return to footnote 57 referrer

Footnote 58

Papineni RS, Rosenthal FS. The size distribution of droplets in the exhaled breath of healthy human subjects. J Aerosol Med. Summer 1997;10(2):105-16. doi:10.1089/jam.1997.10.105

Return to footnote 58 referrer

Footnote 59

Pei LY, Gao ZC, Yang Z, Wei DG, Wang SX, et al. Investigation of the influencing factors on severe acute respiratory syndrome among health care workers. Beijing da xue xue bao Yi xue ban - Journal of Peking University Health sciences. 2006;38:271–275

Return to footnote 59 referrer

Footnote 60

Randall K, Ewing ET, Marr LC, et al. How did we get here: what are droplets and aerosols and how far do they go? A historical perspective on the transmission of respiratory infectious diseases. Interface Focus. 2021;11:20210049. doi:10.1098/rsfs.2021.0049

Return to footnote 60 referrer

Footnote 61

Sajgalik P, Garzona-Navas A, Csecs I, et al. Characterization of aerosol generation during various intensities of exercise. Chest. 2021;160:1377-1387. [PMID: 33957100] doi:10.1016/j.chest.2021.04.041

Return to footnote 61 referrer

Footnote 62

Sickbert-Bennett EE, Samet JM, Clapp PW, et al. Filtration efficiency of hospital face mask alternatives available for use during the COVID-19 pandemic. JAMA Intern Med. 2020;180:1607-1612. [PMID: 32780113] doi:10.1001/jamainternmed.2020.4221

Return to footnote 62 referrer

Footnote 63

Schijven J, Vermeulen LC, Swart A, Meijer A, Duizer E, de Roda Husman AM. Quantitative microbial risk assessment for airborne transmission of SARS-CoV-2 via breathing, speaking, singing, coughing, and sneezing. Environ Health Perspect 2021;129(4):47002.

Return to footnote 63 referrer

Footnote 64

Sheward D, Kim C, Pankow A, et al. Preliminary report – Early release, subject to modification: Quantification of the neutralization resistance of the Omicron Variant of Concern. https://drive.google.com/file/d/1CuxmNYj5cpIuxWXhjjVmuDqntxXwlfXQ/view [preprint]

Return to footnote 64 referrer

Footnote 65

Stadnytskyi V, Bax CE, Bax A, Anfinrud P. The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission. Proc Natl Acad Sci U S A. Jun 2 2020;117(22):11875-11877. doi:10.1073/pnas.2006874117

Return to footnote 65 referrer

Footnote 66

Stadnytskyi V, Anfinrud P, Bax A. Breathing, speaking, coughing or sneezing: What drives transmission of SARS-CoV-2? J Intern Med 2021;(8).

Return to footnote 66 referrer

Footnote 67

Stockwell RE, Ballard EL, O’Rourke P, Knibbs LD, Morawska L, Bell SC. Indoor hospital air and the impact of ventilation on bioaerosols: A systematic review. J Hosp Infect 2019;103(2):175-184

Return to footnote 67 referrer

Footnote 68

Tang JW, Marr LC, Li Y, et al. Covid-19 has redefined airborne transmission [Editorial]. BMJ. 2021;373:n913. [PMID: 33853842]doi:10.1136/bmj.n91

Return to footnote 68 referrer

Footnote 69

Teleman MD, Boudville IC, Heng BH, Zhu D, Leo YS. Factors associated with transmission of severe acute respiratory syndrome among health-care workers in Singapore. Epidemiology & Infection. 2004;132:797–803

Return to footnote 69 referrer

Footnote 70

Tran K , Cimon K , Severn M , et al. Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review. PLoS One. 2012;7:e35797. [PMID: 22563403] doi:10.1371/journal.pone.0035797

Return to footnote 70 referrer

Footnote 71

Trannel AM, Kobayashi T, Dains A, et al. Coronavirus disease 2019 (COVID-19) incidence after exposures in shared patient rooms in a tertiary-care center in Iowa, July 2020-May 2021. Infect Control Hosp Epidemiol. 2021:1-4. [PMID: 34250882] doi:10.1017/ice.2021.313

Return to footnote 71 referrer

Footnote 72

Wilhem A, Widera M, Grikscheit K, et al. Reduced Neutralization of SARS-CoV-2 Omicron Variant Vaccine Sera and monoclonal antibodies. medRxiv 2021.12.07.21267432

Return to footnote 72 referrer

Footnote 73

Wilson NM, Marks GB, Eckhardt A, et al. The effect of respiratory activity, non-invasive respiratory support and facemasks on aerosol generation and its relevance to COVID-19. Anaesthesia. 2021;76:1465-1474. [PMID: 33784793] doi:10.1111/anae.15475 -1474. [PMID: 33784793] doi:10.1111/anae.15475

Return to footnote 73 referrer

Page details

Date modified: