Asked by Anup
Respiratory droplets are referred to droplet particles > 5–10 μm in diameter. It has been regarded that COVID-19's spread is primarily with respiratory droplets and there is controversy about airborne transmission (droplet particles < 5 μm in diameter or droplet nuclei).
A commentary published by Greenhalgh T, et.al. on May 1, 2021 in Lancet has provided 10 scientific reasons in support of airborne transmission as a predominant mode of transmission of SARS-CoV-2 which seems to be very convincing:
- Long-range transmission observed at super-spreader events.
- Long-range transmission has been reported among rooms at COVID-19 quarantine hotels, settings where infected people never spent time in the same room.
- 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.
- Transmission outdoors and in well-ventilated indoor spaces is lower than in enclosed spaces.
- Nosocomial infections are reported in healthcare settings where protective measures address large droplets but not aerosols.
- Viable SARS-CoV-2 has been detected in the air of hospital rooms and in the car of an infected person.
- Investigators found SARS-CoV-2 in hospital air filters and building ducts.
- It's not just humans — infected animals can infect animals in other cages connected only through an air duct.
- No strong evidence refutes airborne transmission, and contact tracing supports secondary transmission in crowded, poorly ventilated indoor spaces.
- Only limited evidence supports other means of SARS-CoV-2 transmission, including through fomites or large droplets.
Greenhalgh T, Jimenez JL, Prather KA, Tufekci Z, Fisman D, Schooley R. Ten scientific reasons in support of airborne transmission of SARS-CoV-2. Lancet. 2021 May 1;397(10285):1603-1605. doi: 10.1016/S0140-6736(21)00869-2. Epub 2021 Apr 15. PMID: 33865497; PMCID: PMC8049599.
