@dashger Well, consider vampires. In a lot of settings, they're pretty much at an advantage over stock humans in many ways if not every way (lot of variation here by setting and all in terms of pros and cons). But it's initially spread by a type of infection or such, usually, and it can even sometimes be cured. Calling it a type of illness at this stage isn't too far off the mark. If eventually everyone were to contract it and it was then passed down more often than not, they might change how they look at it.
That's where the people in this probably are on the catulus thing at the moment. There are some pretty interesting advantages, but they don't know everything about it yet either and it currently seems to be spreading so treating it as an illness for the purpose of studying it at least until it's better understood is pretty fair.