COVID-19 Virus 'Cells' traveling traveling by water particles smaller than "droplets". They're called "Water Aerosol",
.. that is: μm - unit of weight, in micrograms.  1 gram=1,000μm     droplets weigh 5 to 10μm,     aerosols weigh less than 5 μm A large proportion of the spread of COVID-19 occurrs through airborne transmission of aerosols rather than droplets.   Aerosols can:  - Accumulate  - Remain infectious in indoor air for hours  - Be easily inhaled deep into the lungs Measures to reduce aerosol transmission;  Universal masking. Humans produce respiratory droplets ranging from 0.1 to 1000 μm.  Particle size, gravity, and evaporation, determines how far emitted droplets & aerosols will travel in air.  Saliva Droplets will fall faster than they evaporate; contaminating surfaces and leading to contact transmission.  Aerosols will evaporate faster than they can settle. They are buoyant and can be transported by air movement over 6 feet. There are two major respiratory virus transmission pathways:  1. Contact between pe...