When considering how people are infected and what can be done to prevent the infections, answers from many disciplines are sought: microbiology, epidemiology, medicine, engineering, and physics. There are many pathways to infection spread, and among the most significant from the epidemiological point of view is airborne transport. Microorganisms can become airborne when droplets are generated during speech, coughing, sneezing, vomiting, or atomization of feces during sewage removal. The fate of the droplets is governed by the physical principles of transport, with droplet size being the most important factor affecting their dispersion, deposition on surfaces and determining the survival of microorganisms within the droplets. In addition, physical characteristics of the indoor environment as well as the design and operation of building ventilation systems are of critical importance. Do we understand the mechanisms of infection spread and can we quantify the droplet dynamics under various indoor conditions? Unfortunately no, as this aspect of infection spread has attracted surprisingly little scientific interest. However, investigations of numerous cases in which a large number of people were infected show how critical the physics of microorganism spread can be. This paper reviews the state of knowledge regarding mechanisms of droplet spread and solutions available to minimize the spread and prevent infections.
Practical implications: Every day tens of millions of people worldwide suffer from viral infections of different severity at immense economic cost. There is, however, only minimal understanding of the dynamics of virus-laden aerosols, and so the ability to control and prevent virus spread is severely reduced, as was clearly demonstrated during the recent severe acute respiratory syndrome epidemic. This paper proposes the direction to significantly advance fundamental and applied knowledge of the pathways of viral infection spread in indoor atmospheric systems, through a comprehensive multidisciplinary approach and application of state-of-the-art scientific methods. Knowledge gained will have the potential to bring unprecedented economical gains worldwide by minimizing/reducing the spread of disease.