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Malin Alsved

Malin Alsved

Postdoctoral Fellow

Malin Alsved

Airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Hospitals : Effects of Aerosol-Generating Procedures, HEPA-Filtration Units, Patient Viral Load, and Physical Distance


  • Sara Thuresson
  • Carl Johan Fraenkel
  • Sviataslau Sasinovich
  • Jonathan Soldemyr
  • Anders Widell
  • Patrik Medstrand
  • Malin Alsved
  • Jakob Löndahl

Summary, in English

BACKGROUND: Transmission of coronavirus disease 2019 (COVID-19) can occur through inhalation of fine droplets or aerosols containing infectious virus. The objective of this study was to identify situations, patient characteristics, environmental parameters, and aerosol-generating procedures (AGPs) associated with airborne severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus.

METHODS: Air samples were collected near hospitalized COVID-19 patients and analyzed by RT-qPCR. Results were related to distance to the patient, most recent patient diagnostic PCR cycle threshold (Ct) value, room ventilation, and ongoing potential AGPs.

RESULTS: In total, 310 air samples were collected; of these, 26 (8%) were positive for SARS-CoV-2. Of the 231 samples from patient rooms, 22 (10%) were positive for SARS-CoV-2. Positive air samples were associated with a low patient Ct value (OR, 5.0 for Ct <25 vs >25; P = .01; 95% CI: 1.18-29.5) and a shorter physical distance to the patient (OR, 2.0 for every meter closer to the patient; P = .05; 95% CI: 1.0-3.8). A mobile HEPA-filtration unit in the room decreased the proportion of positive samples (OR, .3; P = .02; 95% CI: .12-.98). No association was observed between SARS-CoV-2-positive air samples and mechanical ventilation, high-flow nasal cannula, nebulizer treatment, or noninvasive ventilation. An association was found with positive expiratory pressure training (P < .01) and a trend towards an association for airway manipulation, including bronchoscopies and in- and extubations.

CONCLUSIONS: Our results show that major risk factors for airborne SARS-CoV-2 include short physical distance, high patient viral load, and poor room ventilation. AGPs, as traditionally defined, seem to be of secondary importance.


  • Ergonomics and Aerosol Technology
  • LTH Profile Area: Nanoscience and Semiconductor Technology
  • LTH Profile Area: Aerosols
  • LTH Profile Area: Engineering Health
  • NanoLund: Center for Nanoscience
  • Infection Medicine (BMC)
  • Clinical Virology, Malmö
  • Clinical Microbiology, Malmö
  • EpiHealth: Epidemiology for Health

Publishing year







Clinical infectious diseases : an official publication of the Infectious Diseases Society of America





Document type

Journal article


Oxford University Press


  • Infectious Medicine


  • COVID-19
  • Hospitals
  • Humans
  • Physical Distancing
  • Respiratory Aerosols and Droplets
  • SARS-CoV-2
  • Viral Load



Research group

  • Clinical Virology, Malmö
  • Clinical Microbiology, Malmö


  • ISSN: 1537-6591