In my own career of answering questions, I’ve observed many times that whenever the term “nature” sneaks in, the conversation turns to nonsense. Nature is a cultural construct (and, naturally, a construct of OUR culture), not a veridical reality like the ozone layer or the Coriolis Force. According to this construct, nature has “intentions”—like “trying to restore balance on the planet.”
There is no such entity “trying” to do anything here. During our three or four million years on this planet, we have doubtless been host to many diseases that are now extinct for the simple reason that they killed off all those who were susceptible to them. These diseases didn’t come into existence because “nature” was trying to “do” something. This is just not a useful way to think about these matters.
Smallpox and polio are not “competitors” of ours. They don’t compete with us for space, sunlight, or food (the way that, say, rain forests, coyotes, and mice do). If our civilization (and ultimately our medical science) hadn’t come along, smallpox and polio would eventually have become extinct through their own host-destroying action. It isn’t as though smallpox and polio are capable of living independently of humans (like, say, rain forests, coyotes, and mice are).
Self-defense is a built-in mechanism in every species. Any creature that is attacked by another will defend itself to the best of its ability, and if you were attacked by a lion, you wouldn’t just stand there, thinking, “Well, maybe nature is using this lion to restore balance on the planet.” If you had a rock, you’d defend yourself with a rock; if you had a knife, you’d defend yourself with a knife; if you had a gun, you’d defend yourself with a gun.
The lion doesn’t have a claim on life that is superior to yours—and neither does the AIDS virus. But you can’t defend yourself against the AIDS virus with a rock, a knife, or a gun. The fact that you need a different kind of weapon doesn’t constitute a prohibition against using it (if you can find it). So, if you decide to abandon your interest in virology, please don’t say you did this as a result of reading one of my books!