Although I have not read this specifically, just from the nature of your question, I can tell you this is NOT a myth. A body's fever DOES indeed kill a virus within your body. This is the reason that you should not try to bring your fever down with analgesics or other methods until the fever has reached 104 degrees or higher. G-d is amazing to have given us these bodies that make a fever to fight an infection. The higher temperatures within our body is what helps to eliminate viral and bacterial infections. That's how it works!
