An analytical article on Seznam Zpravy has been published trying to explain why it took the WHO so long to accept that COVID-19 is also spread in the aerosol form. Dr. Vladimír Ždímal from the Institute of Chemical Processes of the CAS commented on the issue, along with several other Czech experts from the ranks of epidemiologists, infectologists, and occupational hygienists. Apparently, a combination of factors is to blame. The most important is probably the lack of communication between experts from different disciplines and the different terminology used in different disciplines for the same phenomenon. Another reason is the great inertia of opinion in the fields, where if an authority establishes a certain dominant way of explaining phenomena, it is difficult to change this approach in subsequent generations, even if experimental data point to a different explanation. Another important reason in this particular case is that the spread of respiratory diseases is a dynamic process so that even when infected persons emit fine droplets, near their mouths the water evaporates from the droplets and continues to be transported as an aerosol. Therefore, it is inappropriate to simultaneously categorise diseases as those that are transmitted in the form of droplets and others in the form of aerosols. Very often it is a combination of both. The advantage of aerosol science is that it considers both large droplets and small dried particles as aerosols, differing only in size due to their water content. Therefore, of all disciplines, aerosol physics was the earliest to recognize aerosol transmission as an important form of disease spread but failed to transfer this information to the medical, epidemiological, and infectious disease communities.
Pic. 1: In the picture you can see large droplets, however, Covid-19 is spread even by smaller particles that cannot be seen visually (aerosol). Foto-Profimedia.cz.