Throughout history, humans have existed side-by-side with bacteria and viruses. From the bubonic plague to smallpox, we have evolved to resist them, and in response they have developed new ways of infecting us.
We have had antibiotics for almost a century, ever since Alexander Fleming discovered penicillin. In response, bacteria have responded by evolving antibiotic resistance. The battle is endless: because we spend so much time with pathogens, we sometimes develop a kind of natural stalemate.
However, what would happen if we were suddenly exposed to deadly bacteria and viruses that have been absent for thousands of years, or that we have never met before?
We may be about to find out. Climate change is melting permafrost soils that have been frozen for thousands of years, and as the soils melt they are releasing ancient viruses and bacteria that, having lain dormant, are springing back to life.
In August 2016, in a remote corner of Siberian tundra called the Yamal Peninsula in the Arctic Circle, a 12-year-old boy died and at least twenty people were hospitalised after being infected by anthrax.
The theory is that, over 75 years ago, a reindeer infected with anthrax died and its frozen carcass became trapped under a layer of frozen soil, known as permafrost. There it stayed until a heatwave in the summer of 2016, when the permafrost thawed.
This exposed the reindeer corpse and released infectious anthrax into nearby water and soil, and then into the food supply. More than 2,000 reindeer grazing nearby became infected, which then led to the small number of human cases.
The fear is that this will not be an isolated case.