USDA confirms that reheating can kill bacteria if heated to the proper temperature and IF THE FOOD WASN'T KEPT OUT OVER 2 HOURS PRIOR TO REFRIGERATION. Eating the food that has been left out can cause food borne illnesses like staphylococcus when bacteria can grow when it's in the danger zone of 40°F and 140°F. It is best to reheat to 165 degrees Fahrenheit. If you experience symptoms as: vomiting, upset stomach, fever, nausea or diarrhea, err on the side of caution and go to an urgent care to see if you have food borne illness such as salmonella.