If you’re trapped in a building, it’s probably not the best time to start setting fire to things. But this is exactly what some bacteria do when they find themselves in a human; they cause diseases that are potentially fatal but not contagious. Without an escape, they risk going down with their host. This seems like a ludicrous strategy but we’re looking at it from the wrong perspective – our own. In truth, humans often have nothing to do with the diseases that plague us; we’re just collateral damage in an invisible war.
Like all living things, bacteria have to defend themselves against predators like amoebas. Some species do so using resistance genes that turn them from passive victims into aggressive fighters. And by coincidence, these same adaptations make them more virulent (good at causing disease) in human bodies. We’re just caught in the crossfire.