What are the odds of my son getting sick from eating an 8-day old hamburger?

There are good chanc: Nobody can tell exactly what percent chances of getting sick as there are other factors as to how long the hamberger was out and was it properly referigerated and how it was cooked and recooked and how old the child is but now he has eaten it, all you can do is observe him for abdominal pain, diarrhea, vomiting and feve.If he gets any symptoms than get him treated.

Good chance: There is a good chance, but the best thing to do is to watch and see how the child is acting. Tylenol (acetaminophen) can be given for fevers, but if symptoms worsen, you should see your family practice physician.

Time will tell.: Food poisoning can result from eating improperly handled or inadequately cooked meat. He may develop some nausea, vomiting and diarrhea. That was a bad idea.