We humans tend to regard ourselves as the masters of the world. But we are simply part of the ecosystem. There are more bacteria cells in and on our bodies than human cells. There are enormous amounts of viruses in and on our bodies as well.
We treat microbes as harmful in general. That is why we actively sterilize our environment. But most microbes around us are beneficial to us overall. Bacteria help us digest. Many viruses eat bacteria, preventing those bacteria from multiplying exponentially inside humans. The most potent antibiotics are produced by fungi. Penicillin, the most widely used antibiotics, is produced by Penicillium, a type of fungi. If antibiotics kill too many bacteria, fungi will overrun human bodies, for harmful fungi are no more checked by bacteria. Different kinds of microbes, by constraining each other, keep humans healthy most of the time.
Some bacteria probably do more harm than good. We try very hard to eliminate them or reduce their presence. We are more successful in developing vaccines or treatments against DNA based organisms, which are more stable and easier to target. But RNA viruses mutate very fast. It is more elusive to target the ever changing RNA viruses accurately. Many recent epidemics, such as HIV, influenza, and coronaviruses, are caused by RNA viruses.
When we suppress one type of microbe, we celebrate our success. But from the ecological perspective, we merely open a rich ecological niche, human bodies, for new hosts. This is why superbugs flourish in hospitals, where most known microbes are suppressed. When we eliminate one type of bacteria, it makes it easier for those weaker and less competitive pathogens to invade us. RNA viruses mutate very often. They make so many mistakes. It is very difficult for them to compete with more stable, more powerful DNA organisms. But when humans eliminate DNA organisms, RNA viruses face less competition. It is we ourselves who make RNA viruses such successful invaders.
Are we hopeless facing microbes? We really need to assess our situation from a bigger picture, from a longer time frame. Are microbes our biggest threat? Not really! From ecological perspective, any society with below replacement fertility is doomed. The biggest threat to our society is the below replacement fertility. What is the cause for such a low fertility? There can be several reasons. One could be the overdrive of our immune systems in a sterile environment. When our immune systems face less external invaders, they often turn to our own cells. This could be the reason more auto immune diseases occur in clean environment. Women’s immune systems could also attack the cells of fetuses. There are evidence that the existence of some parasites is correlated to higher fertility rate.
From the ecosystem perspective, our war against microbes is futile over long term. In a society which could not reproduce itself, such a war is counterproductive.