It is important to point out, though, that there is no intelligence behind evolution, nor are viruses capable of thought. They are mere bundles of genetic instructions which call for their own duplication, a process that, like typing in a handwritten letter, lends itself to typos, i.e. mutations. It is thus hazardous to think of any virus as having a will to survive and of thus wanting for its host to cling to life long enough to help spread the little bugger. The avirulence theory beguiles our desire to anthropomorphize the billions and billions of viruses on our planet.

But in truth, there is no grand design; instead, there are forces that act on both viruses and hosts. Our scientific understanding eventually moved beyond the avirulence theory and into more nuanced thinking: that it was all about trade-offs.

Tuberculosis has been with us for hundreds of years and it is still deadly. Dengue fever’s own virulence has risen over the last decades. And the myxoma virus, slayer of rabbits? It too has grown deadlier fangs, according to limited data from the 1980s, with a larger percentage of circulating virus in Australia being highly virulent compared to the previous decade. The universality of avirulence theory simply has too many contradictions. Viruses don’t always evolve to become benign.