We have so many individuals to be thankful for when it comes to advances in healthcare. From the author of the Kahun medical papyrus, dated at 1800 BCE (and thought to be a copy of an even older document), to the modern-day scientists developing genetically-based cancer treatments, the history of medical science is rich with brilliant innovators. Alas, not all of those innovators were celebrated in their day, while others were even vilified.
We are all covered in bacteria. (You could even say we are all contaminated.) Bacteria and other microorganisms live in our gut, in our mucous membranes such as our nostrils, on our eyelashes, and in our bellybuttons. We do not consider ourselves infected, however, because these organisms have not crossed the barrier of our skin to enter our tissues, muscles, bones, and body cavities. These deep parts of our bodies are basically sterile - no microorganisms live there at all. As long as our protective barriers are not breached, we remain healthy. The "contamination" is just part of our microbiome, our own personal little collection of life that we carry around with us all the time. This microbiome is made up of colonies of bacteria, groups of same-species bacteria that live and die without our even being aware of them.
Bacteria are single-cell organisms. Where humans are made up of, on average 1 trillion cells, bacteria are made up of just one. But one isn't the loneliest number when it comes to bacteria; they reproduce very efficiently by splitting into two, who then go on to split into two more… and on until you have a colony of bacteria. Some of these colonies are beneficial to us, some don't harm us at all, and some are downright nasty, leading to harmful infections which can threaten our lives.
