 [ Symptoms ] what are the systems of the flu is ear ache one [ Disease ] influenza also known as the flu is a contagious respiratory illness caused by flu viruses it can cause mild to severe illness and at times can lead to death the flu is different from a cold the flu usually comes on suddenly people who have the flu often feel some or all of these symptoms • fever* or feeling feverishchills • cough • sore throat • runny or stuffy nose • muscle or body aches • headaches • fatigue tiredness • some people may have vomiting and diarrhea though this is more common in children than adults * it is important to note that not everyone with flu will have a fever most people who get influenza will recover in a few days to less than two weeks but some people will develop complications such as an ear infection as a result of the flu pneumonia bronchitis sinus and ear infections are examples of complications from flu