According to current evidence, COVID-19 virus is primarily transmitted between people through respiratory droplets by direct contact with infected people and indirect contact with surfaces that are exposed to droplets from an infected patient.
Droplets come in different sizes. Typically, respiratory droplets are 5-10µm (around the size of a red blood cell) and may travel over the distance up to 1 meter. When droplets are less than 5µm, they are referred to as aerosol. Given the light weight, aerosol may travel in the air over up to 50 meters from its source.
Airborne transmission occurs when microbes within the droplet aerosol remain in the air for long periods of time, before infecting a healthy person through inhalation. In the context of COVID-19, airborne transmission may be possible in specific circumstances and settings in which procedures or support treatments that generate aerosols are performed.
And even these COVID-19 aerosols do not directly infect a healthy person, there is still a chance that they might fall on surfaces and be exposed to those who touch the contaminated object.
To date, WHO suggests that there is no available evidence of airborne transmission of COVID-19. However some outbreak reports related to indoor crowded spaces have suggested the possibility of aerosol transmission, combined with droplet transmission, for example, during religious service, restaurants or in fitness classes.
Although further study is still needed to elucidate the possibilities of airborne transmission, precautions are to be taken seriously.
Most disinfection treatments have emphasized on surface deep cleaning and hand hygiene. However, to anticipate the developing modes of COVID-19 transmission, it is very important to increase indoor air sanitation against viruses and other infectious pathogens.