My Son Was Away On A Camp And They Were

My son was away on a camp and they were exposed to eating red meat that was not fully cooked and placed into a container after it was cooked with raw meat. He was vomiting and had diarrhea the next day. The vomiting has stopped the following day but he still had sever stomach cramps. He then noticed that his gums are swollen and painfull. This is the third day after the camp he still has swollen gums and feels very weak. Have been sticking to the basics, no milk products, take in a lot of fluids and just eating small amounts. What else can I give him to help reduce the cramping and the swollen gums? Thanks