Why do some meat be cooked medium rare but others have to be fully cooked?

At last! A fascinating subject for a discussion! Congratulations to the poster. I don't know the answers but can only give my opinion. I believe rare cooked meats of any kind are unsafe to eat. Salmon, as with many fish, can be rather dangerous even when fully cooked. It depends on its age (after being caught) and how it was stored. Perhaps beef is just a little safer because cows suffer from fewer diseases compared to chickens and pigs. But having said that, foot and mouth disease is pretty nasty! I am someone who eats steak very well done and my salmon is cured and smoked. So, do I take any risks with food? Yes, mussels are my favorite seafood. They turn to rubber if overcooked and explode in the microwave, so you have to eat them lightly cooked. Luckily, I haven't got sick lately. I look forward to hearing some expert opinions on this subject.