1800 distinct varieties in the air of San Antonio and Austin, from sewage microbes to human gum microbes all floating in the air, take a deep breath can you taste it? Chinese microbes make their way here, too. Snowflakes are based on microbes finding an ice nucleator, snowflakes are alive.
A deadly strain is in your nose, that strain is like the jihadis or white supremacist gun nuts. Harmless unless it is let out and given untrammeled freedom. Staph in your nose is harmless, but it can morph into a superstrain of bacteria resistant flesh eating bacteria, or septic shock, it can infect IVs and other hospital equipment.
Many airborne microbes haven’t come from very far away, but some have traveled enormous distances. Dust from deserts in China moves across the Pacific to North America and east to Europe, eventually circling the globe. Such dust clouds harbor bacteria and viruses from the soils where they originated, as well as other microbes they pick up from the smoke of garbage fires or from the mist above the oceans they cross. Take a breath, and you sample the world.
Above the air we breathe, the upper atmosphere also contains microbes, floating as high as 22 miles above Earth’s surface. I believe they could go even higher, though it’s hard to imagine they could live long so far from water and nutrients. Lower down, they appear to survive and even thrive. There is evidence that despite high levels of ultraviolet radiation that would kill most bacteria, some metabolize and perhaps even reproduce inside clouds. In fact they may play a part in the formation of snowflakes that require a nucleator, or small particle, to crystallize around. In 2008 Brent Christner of Louisiana State University and his colleagues showed that microorganisms were the most efficient ice nucleators present in snow. That’s right—snow is literally alive.