Most of us in the developed world spend the majority of our time indoors, breathing clean-smelling air that is mechanically warmed or cooled and then perhaps filtered and recirculated. Windows are usually shut, especially in modern commercial structures such as hospitals. In the Unites States, the norm in patient rooms are inoperable windows, so when you are an in-patient, you have no choice about the source of your inhaled air.
Thanks to incredible new techniques that allow scientists to map the DNA and RNA "fingerprints" of bacteria, viruses, and fungi, we now know that these microbes are everywhere — in and on our bodies, in the air, water, buildings, and outdoors. Knowledge about these microbial ecosystems, referred to as microbiomes, is increasing by the week! We now know that in number, each of us is only from 10-30% human cells, the rest of us consisting of approximately 3 lbs of viruses, bacteria, and fungi, living on or inside us. Our microbiome impacts every aspect of our health, from digestion to psychological stability to immunological protection from infections and allergies.