Top 10 reasons backing airborne transmission of COVID-19

  1. The dominance of airborne transmission is supported by long-range transmission observed at super-spreader events.
  2. Long-range transmission has been reported among rooms at COVID-19 quarantine hotels, settings where infected people never spent time in the same room.
  3. Asymptomatic individuals account for an estimated 33% to 59% of SARS-CoV-2 transmission, and could be spreading the virus through speaking, which produces thousands of aerosol particles and few large droplets.
  4. Transmission outdoors and in well-ventilated indoor spaces is lower than in enclosed spaces.
  5. Nosocomial infections are reported in healthcare settings where protective measures address large droplets but not aerosols.
  6. Viable SARS-CoV-2 has been detected in the air of hospital rooms and in the car of an infected person.
  7. Investigators found SARS-CoV-2 in hospital air filters and building ducts.
  8. It is not just humans — infected animals can infect animals in other cages connected only through an air duct.
  9. No strong evidence refutes airborne transmission, and contact tracing supports secondary transmission in crowded, poorly ventilated indoor spaces.
  10. Only limited evidence supports other means of SARS-CoV-2 transmission, including through fomites or large droplets.


1.)  Covid-19 has redefined airborne transmission. BMJ 2021; 373 doi: (Published 14 April 2021) Cite this as: BMJ 2021;373:n91