Viruses

There are some examples where viruses have become more mild, and there are some reasons why that might happen. We usually also can't separate the changes in the host from the changes in virus. As we become more immune, even the same virus will cause less severe disease. More mild and completely harmless are very different things. And thatat really the part that we can control, is our immunity. That is almost always a beneficial thing in terms of virulence of the virus.