Is this food poisoning? The flu?

Earlier today, my 18 yr. old ate some old cooked chicken that had been in the freezer for a long time. About 6 hours later he began to have lower abdominal pain. Later in the day, the pain subsided but now he has muscle and joint pain, a headache, and is running a fever. No diarrhea, no vomiting, no nausea. Could this be food poisoning anyway? I know it can begin as soon as 30 min. after ingesting contaminated food and it can cause a mild fever, but without the other typical symptoms I'm wondering just what he has.