Background
Epidemiology of COVID-19 in healthcare workers
Transmission pathways
What is the evidence for SARS-CoV-2 transmission via aerosols?
Reproductive number, superspreading events and asymptomatic transmission
Infectious droplets and aerosols
Clinical evidence for true aerosol transmission of SARS-CoV-2 in humans?
SARS-CoV-2 transmitted by droplets with a range > 2 m
“Aerosol-generating procedures” (AGP)
Procedure | Point or Pooled estimate (OR, 95% CI) |
---|---|
Tracheal intubation (4 cohort studies & 4 case-control studies) | 6.6 (2.3–18.9) & 6.6 (4.1–10.6) |
Non-invasive ventilation (2 cohort studies) | 3.1 (1.4–6.8) |
Tracheotomy (1 case-control study) | 4.2 (1.5–11.5) |
Manual ventilation before intubation (1 cohort study) | 2.8 (1.3–6.4) |
Mask types to protect HCW from COVID-19 transmission
Surgical masks versus respirators
Certification/ Class (Standard) | FFP2 (EN 149) | Type II Surgical Mask (EN 14683) |
---|---|---|
Protection | Protection of the carrier against solid and liquid aerosols | Protection against droplet ejection from the carrier* |
Application | Self protection / Industrial safety | External protection* |
Filter performance – (must be ≥ X% efficient) | 0.3 Microns ≥94% | 3.0 Microns: ≥ 98% 0.1 Microns: No requirement |
Total inward leakage | ≤ 8% leakage (arithmetic mean) | No requirement |
Exposure to of inert particles and live aerosolised influenza virus | Estimated 100-fold reduction** | Estimated 6-fold reduction** |
Indirect evidence consistently supports the use of surgical masks
When mask protection seems to fail
Study | Included Patients (n) | Randomization | Incidence of laboratory-confirmed influenza infection | |
---|---|---|---|---|
Mask | Respirator | |||
Loeb, 2009 [52] | 446 | Individual | 22.2% | 21.7% |
MacIntyre, 2011 [53] | 1441 | Cluster | 1.2% | 0.4% |
MacIntyre, 2013 [43] | 1669 | Cluster | 0.3% | 0.5% |
Radanovich, 2019 [54] | 2862 | Cluster | 7.3% | 8.3% |