GERMS STAY BAD
In high school biology classes, we routinely teach the concept of Darwinian evolution, or what is often called “survival of the fittest.” Darwinian principles apply to all life forms—from the lowliest of bacteria to complex multi-cellular mammals. But for many years, the principles have often been misapplied, even by experts. An understanding of these concepts is necessary in order to appreciate the highly dynamic nature of evolution in microorganisms. Their ability to rapidly multiply allow them to adapt to new hosts—and develop resistance to medicines—with frightening speed.
It is helpful to begin with a misnomer, one that we are all taught in school. It goes like this: Bacteria and viruses become more and more benign the longer they are in contact with their host populations. In other words, organisms adapt toward a symbiotic (i.e., cooperative) relationship with their hosts. This, we were told, explains why serious infectious diseases were on the wane in many places in the world.
It is the also the explanation for why, in certain settings like refugee camps, there would inevitably be a sudden explosion in cases of diarrhea that would slowly dissipate as the organism “learned to adapt” to its hosts— because by killing its hosts the organism was depriving itself of new victims.