Law of declining virulence

Law of declining virulence means that over time a disease or virus will become less serious and less deadly. This is because the virus or disease changes and adapts over time so that it isn't as harmful to people. The same virus can be around for a long time but it is not as strong or dangerous as it used to be. It's like when you're sick and you take medicine to make you feel better; after a while, you will be healthy again. A virus becomes weaker in a similar way.