"Leper at a baseball game (really sick)" joke

This leper goes to a baseball game and sits in a fairly empty section so the people around him won't have to look at his condition. Just before the game starts a guy sits in the row behind him, and another sits a few rows back.

About the third inning the guy a few rows back turns to the side and vomits all over the seat next to him. The leper turns around and begins to apologize, "I'm sorry, I will move, I know that it was because of my horrible condition that you just vomited," to which the guy replies, "No, no, it isn't you, I swear." Still not completely satisfied, the leper turns around.

Two innings later the guy does it again, vomits on the seat next to him. Again the leper turns around and says, "I appreciate that you're not saying anything, but I can tell that you're disgusted and I will move to a different seat." The guy gives the same response, swearing it isn't the leper that's upsetting his stomach.

During the seventh inning stretch the guy vomits again and the leper turns around.

"It isn't me, you say?" he asks.

"No, it isn't you, I swear," the guys says.

"Well if you don't mind me asking, what is it?" ask the leper.

"Oh, it's not you," the guy says. "It's the guy behind you, dipping his nachos in your back.