I remember when I caught a sick rat and I didn't know what to do with it

so I took it to the vet in a shoe box. I gave it to the vet and said, "I found this and don't know what to do." The vet looked at me in a way like "are you serious?" but saw I was serious so he shook his head and smiled at me and took the shoe box with the rat and said he'd take care of it for me. Lol. That vet is a nice man, he did a house visit for me when it was time to put Jazz to sleep and he nearly cried for me, he teared up.

honest question. why woulld you pick up a sick rat? what if it had parasites or rabbis or something? if it had bitten you, you could have gotten really sick and started foaming at the mouth, posting angry things on the interent