Table 1

Studies in support of airborne transmission of respiratory pathogens

StudyCountry, SettingPathogenType of ventilationInfection identified byMain findings
Lu et al31China, restaurantSARS-CoV-2Mechanical: standalone air conditioner (A/C)Clinical diagnosis; unspecifiedDevelopment of symptoms in 12% of diners in the vicinity of the index patient; viral droplets propagated by A/C airflow
Kulkarni et al32UK, hospitalRSVMechanical: centralised, unspecifiedPCR diagnosisVirus-laden aerosols from index patient were present within 10 m radius, remained for 2 hours after the patient was discharged and infected respiratory epithelial cells in vitro
Wong et al33Hong Kong, hospitalInfluenzaMechanical: with HEPA filter close to index patientRNA sequencingImbalanced airflow pattern facilitated infection transmission; identical viral strain in the index patient and contacts
Li et al34Hong Kong, hospitalSARS-CoV-1Mechanical: central air conditioningUnspecifiedCFDS showed an association between the concentration decay from the index patient’s bed and the spatial SARS infection pattern involving 138 people
Yu et al35Hong Kong, multifloor apartment complexesSARS-CoV-1Natural and mechanical: central circulation systemUnspecifiedExperimental studies showed that aerosols were generated and drawn in by an exhaust fan from contaminated sewage leading to infections on multiple floors
Olsen et al36Taiwan, aircraftSARS-CoV-1Mechanical: aircraft ventilationRT-PCR and serologyProximity-dependent viral spread from a symptomatic host in aircraft
Jiang et al20China, hospitalSARS-CoV-1Natural and mechanicalUnspecifiedIncreased rate of HCW infection with a lower ratio of window size to room volume and laminar air flow mechanical ventilation but no (or closed) windows
Hoge et al37USA, jailStreptococcus pneumoniaeMechanical: HVACCulture and enzyme immunoassayIncreased incidence of pneumococcal disease (identical strain) with overcrowding and decreased outside air delivery by the ventilation system
Shigematsu and Minowa38Japan, buildingTuberculosisMechanical: central air conditioningUnspecifiedIndoor infection of tuberculosis attributed to interrupted ventilation leading to high carbon dioxide concentrations
Bloch et al39USA, paediatrician officeMeaslesMechanical: HVACPhysician diagnosesMeasles outbreak in an office with a high volume of recirculated air via the dispersion of droplet nuclei from the index patient
Moser et al
USA, aircraftInfluenzaMechanical: interrupted aircraft ventilationCulture and serologyInfluenza outbreak-associated air travel with 3 hour interruption in aircraft ventilation; similar strain in 26% of contacts
Ehrenkranz and Kicklighter41USA, hospitalTuberculosisMechanical: central air conditioningMantoux testTuberculosis outbreak associated with recirculation of air-containing droplet nuclei and lack of high-efficiency filters
Wehrle et al42Germany, hospitalSmallpoxNatural ventilationPhysician diagnosisOutbreak of 17 cases of smallpox mediated by air currents and low relative humidity
  • CFDS, computational fluid dynamic simulations; HCWs, healthcare workers; HVAC, heating ventilation and air conditioning system; MERS-CoV, Middle East respiratory syndrome-related coronavirus; RSV, respiratory syncytial virus; RT-PCR, real-time PCR; SARS-CoV-1, severe acute respiratory syndrome coronavirus 1; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.