IT WAS a revelation. Germs cause disease. When Louis Pasteur and Robert Koch discovered and developed what would later be called the germ theory in the 1860s, this was a radical, then revolutionary idea – one so good it seems obvious in retrospect.
At the heart of their work was the notion that individual species cause disease by invading our bodies. Over the next century, the notion of “germs” changed our behaviour. It led us to scrub our hands and actively fight specific pathogens (as researchers came to call dangerous germs) and to cure the diseases they cause. These changes saved millions, maybe billions of lives. Every day you rub shoulders with the success of this theory. How could there be anything wrong with it?