A group of symptoms that are similar to those caused by the influenza (flu) virus. These include fever, chills, headache, muscle or body aches, cough, sore throat, runny nose, fatigue, nausea, vomiting, and diarrhea. Flu-like syndrome may be caused by viral infections or other illnesses that are not caused by the influenza virus. It may also occur as a side effect of certain types of anticancer therapy, especially biological therapies, such as interferon or interleukin. Also called flu-like symptoms.