Chicken and pork, 2 meats they reckon when under cooked can make you crook. Lets face it, have you ever been asked if you'd like your chicken ... well done, medium or rare.
Also, I saw on some TV show that this is a common easy problem. You prepare the chicken on a board and later cut up some salad on the board and the raw chicken juice can make you crook. So wash up everything and no cutting raw chicken then cutting salad etc.
Did you maybe take a drink from a tap or hose?