Title. Basically make a disease have some guaranteed symptoms and some random ones. Because fighting a disease with total organ failure is going to be quite different then fighting one with coughing and insomnia. And add new measures to stop suspific traits. And make some disease classes have a higher likelihood of some traits. For example the prion would have a higher chance of things like insanity. And bio-weapon would have a higher change at things like hemorrhagic shock and total organ failure.