The browser you are using is not supported by this website. All versions of Internet Explorer are no longer supported, either by us or Microsoft (read more here:

Please use a modern browser to fully experience our website, such as the newest versions of Edge, Chrome, Firefox or Safari etc.

Jakob Löndahl

Jakob Löndahl

Associate Professor / Senior Lecturer

Jakob Löndahl

Size distribution of exhaled aerosol particles containing SARS-CoV-2 RNA


  • Malin Alsved
  • David Nygren
  • Sara Thuresson
  • Carl Johan Fraenkel
  • Patrik Medstrand
  • Jakob Löndahl

Summary, in English

Background: SARS-CoV-2 in exhaled aerosols is considered an important contributor to the spread of COVID-19. However, characterizing the size distribution of virus-containing aerosol particles has been challenging as high concentrations of SARS-CoV-2 in exhaled air is mainly present close to symptom onset. We present a case study of a person with COVID-19 who was able to participate in extensive measurements of exhaled aerosols already on the day of symptom onset and then for the following three days. Methods: Aerosol collection was performed using an eight-stage impactor while the subject was breathing, talking and singing, for 30 min each, once every day. In addition, nasopharyngeal samples, saliva samples, room air samples and information on symptom manifestations were collected every day. Samples were analyzed by RT-qPCR for detection of SARS-CoV-2 RNA. Results: SARS-CoV-2 RNA was detected in seven of the eight particle size fractions, from 0.34 to >8.1 µm, with the highest concentrations found in 0.94–2.8 µm particles. The concentration of SARS-CoV-2 RNA was highest on the day of symptom onset, and declined for each day thereafter. Conclusion: Our data showed that 90% of the exhaled SARS-CoV-2 RNA was found in aerosol particles <4.5 µm, indicating the importance of small particles for the transmission of COVID-19 close to symptom onset. These results are important for our understanding of airborne transmission, for developing accurate models and for selecting appropriate mitigation strategies.


  • Ergonomics and Aerosol Technology
  • LTH Profile Area: Aerosols
  • Metalund
  • NanoLund: Center for Nanoscience
  • MERGE: ModElling the Regional and Global Earth system
  • Translational infection medicine
  • Infection Medicine (BMC)
  • Clinical Virology, Malmö
  • EpiHealth: Epidemiology for Health

Publishing year







Infectious Diseases





Document type

Journal article


Informa Healthcare


  • Infectious Medicine


  • cascade impactor
  • COVID-19
  • exhaled aerosol
  • SARS-CoV-2
  • size distribution



Research group

  • Translational infection medicine
  • Clinical Virology, Malmö


  • ISSN: 2374-4235