You can't see them or feel them, but millions of airborne viruses are wafting around you each day, and billions more microbial travelers are descending everywhere on Earth, after riding air currents around the world.

For the first time, scientists have analyzed the vast quantities of viruses that are swept up and swirling about in the atmosphere, sometimes traveling thousands of miles from their point of origin before seeing the planet's surface again. To do that, researchers looked at a boundary layer in the atmosphere — the free troposphere, which lies below the stratosphere but is still high enough to be beyond the reach of weather systems.

https://www.livescience.com/61689-viruses-fall-from-sky.html