Since there is no adequate treatment for COVID-19, prevention of the transmission of SARS-CoV2 is the best way to cope with the pandemic. National guidelines for non-pharmaceutical interventions focus mainly on the interference with viral transmission via droplets and surface by hygiene measures, limitation of human contact, and social distancing. There is growing evidence that a third route of transmission by aerosols - exhaled tiny particles with viable infectious virus that remain airborne for hours - may be relevant. This route may even be the predominant way of viral transmission in the case of so-called superspreading events. It implies the need for adequate ventilation at indoor spaces without recirculation of virus containing aerosols. Here, the use of face-masks might be of added value too. These measures appear to be especially pivotal during episodes of colder weather, when people spend significantly more time indoors.