It has a much shorter lifespan thus in one human lifecycle it has a much more time to evolve. Humans (or other higher animals) are not powerless. They have sex

It has a much shorter lifespan thus in one human lifecycle it has a much more time to evolve. Humans (or other higher animals) are not powerless. They have sex. The random recombination of genes when reproducing can create an environment hostile to parasites/viruses in its offspring. See https://en.m.wikipedia.org/wiki/Red_Queen_hypothesis https://en.m.wikipedia.org/wiki/Red_Queen_hypothesis for details.