Experts state that studies should be focused on clarifying the mechanism of viral aerosol generation and survival, and fully understanding the transmission mechanism of infectious diseases, so as to formulate prevention and control strategies for the COVID-19 pandemic and other newly emerging pathogens. A latest study investigated this matter further.
Many respiratory viruses can spread via contact and droplet transmission but increasing epidemiological data have shown that viral aerosol is an essential transmission route of COVID-19 and influenza virus due to its ability to spread rapidly and high infectiousness.
Aerosols have the characteristics of small particle size, long-time suspension and long-distance transmission, and easy access to the deep respiratory tract, leading to a high infection risk and posing a great threat to public health.
The question remains, does COVID-19 spread between direct infection from person to person or indirect infection through the accumulation of infectious aerosol particles indoors?
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The paper which was written at the suggestion of the interdisciplinary Commission for Pandemic Research of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) aimed to find the best method to guard against infection.
The researchers involved combined findings from different academic fields so as to compile differentiated yet concrete, situation-based knowledge, since at the present time only about 70 percent of the population is sufficiently informed about infectious aerosols – and those who are less well informed do less to guard against infection.
The measures recommended in the paper also consider the relevant recommendations issued by the Robert Koch Institute (RKI), the Center for Disease Control and Prevention (CDC) and the World Health Organisation (WHO).
The study noted: “Both direct and indirect infections can occur inside closed rooms.
“This is why comprehensive precautions are required to guard against infection indoors.
“Outside closed rooms – i.e., in the open air – virtually the only possibility of becoming infected is by direct means: indirect infection is highly unlikely due to the extensive dilution of the viral load and its rapid removal by air currents.”
The study found that these and other factors are involved in the transmission of SARS-CoV-2 inside and outside closed rooms; the researchers also offer concrete advice – relating to protective measures – such as window ventilation, permanently installed ventilation systems, and mobile air purifiers as well as the wearing of particle-filtering masks.
Scientists had earlier warned about airborne transmission by aerosols.
In April last year a scientific panel sent a letter to the White House saying that “studies are consistent with aerosolisation from normal breathing”.
In July, two scientists published a commentary in Clinical Infectious Diseases said it was time “to recognise the potential for airborne spread”.
They continued: “There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale) and we are advocating for the use of preventive measures.”