Possibly dumb question but here goes...

My nephew, who is in the process of being potty trained, was over at my house and managed to get his own urine all over his hands when there was a "spill" on the floor and he decided to play in it. Anyway, my sister was cleaning up the mess on the floor and had not gotten to his hands yet when he wandered over to the cat bowls. He picked up some pieces of food and began feeding it to one of my cats (the one that isn't terrified of him). My cat will eat food out of people's hands, and he thinks this is hilarious and laughs like crazy. I walked into the room not knowing what had happened and thought it was cute until my sister walked in the room with a towel to clean the pee off of my nephew's hands!

I am worried that my cat could get sick from this. I know that people can contract diseases like hepatitis when cooks prepare food without washing their hands after using the restroom. Can cats contract diseases from human urine and feces?

Urine is sterile (unless there is an infection).  I would say there is no need for worry.  

I agree, should be sterile. What is amazing is that your cat would take food from the little tike even when his hands had his own pee smell on them!  It must be love. 

Right, pee is OK - feces is not.

They had to drink their own urine on the way back the camps or die of thirst so not harmful.

Do you think your nephew has hepatitis? I'm sure cats can contract certain diseases from human waste (diseases aren't spread through urine though) but I'm guessing the little guy is pretty disease-free. Should be fine.