Conclusion

In summary, large droplets settle quickly in the vicinity of the ejection point with little drying, whilst small droplets, less than about 100 µm, quickly dry and remain airborne. This has two major implications for public health: firstly, safe distance is considerably longer than the generally-recommended two metres, as the virus remains fully suspended in air. Secondly, mask filters available to the public are inefficient in preventing SARS-CoV-2 spreading, as it is most penetrative through fabric filters. They can retain the droplets from nasal and throat secretions on coughing and sneezing, but cannot protect a person from inhaling nearby viruses released into the atmosphere. The deadliness of this virus has drawn deservedly great attention of the scientific community on its spreading mechanism, with the latest re-evaluation of the basis adopted by the World Health Organization and other agencies (9).