For rebooting business and academic activities in the ongoing COVID-19 pandemic scenario, it is important to pay detailed attention to all forms of infection transfer mechanisms during interaction of people in enclosed environments. In this context, a matter of specific concern will be the possibility of aerosol mediated infection transfer in indoor spaces, which will be largely governed by the size distributions of virus laden droplets, termed as virusols in this work, ejected from humans. We expand on the well-known theory of Poisson fluctuations which acts as statistical barrier against formation of virusols. Analysis suggests that for viral loads of less than 2x105 RNA copies/mL, often corresponding to mild-to-moderate cases of COVID-19, droplets of diameter <20 micron are unlikely to be of consequence in carrying infections. Cut-off diameters below which droplets will be practically free of contamination, are presented as a function of viral loading. The median diameters of virus laden droplet distributions will be 1.5 to 20 times higher depending upon the Geometric Standard Deviation of the droplet size distributions. The studies have implications to residence time estimates of airborne infections in indoor air and for performance evaluation of sanitation and control technologies to mitigate infection risks in workplaces.