– easier to catch a virus (ex. corona, influenza) in winter than in summer
– that our breath condenses into droplets in the cold air.
– humidity helps a virus spread, in winter it is higher than in summer
TU Wien (Vienna), in cooperation with the University of Padova research, has studied air that an infected person exhales when sneezing. They found that the infectious viruses are in liquid droplets of different sizes, with gas in between. The lab experiments used high-speed cameras and computer simulations to identify size and flow. They noted as each droplet burst an increase of humidity occurs, making the remaining droplets evaporate more slowly.
This naturally affects the flow and how long droplets hover.
This research can impact what exactly is social distancing. I believe from my review of the literature it is more than 6 feet. Furthermore, this sort of research and its results will impact the use and type of mask. I will be watching publications for more on this.