When the Apostle Paul exhorted us to be hospitable (see 1 Peter 4:9 for example), I doubt he had microbes in mind. But God might have. We’re host to trillions of the little creatures—on our skin, in our gut, flowing through our veins, and in all of those moist and warm cavities our bodies possess. In fact, they’re in every part of us. And that’s a good thing.
The National Institute of Health’s 2014 Human Microbiome Project concluded that “10,000 microbial species occupy the human ecosystem.” That’s species, not individuals. Other estimates put that number much higher, with 40,000 species of bacteria in our gut alone.