Thw flu is strictly speaking a respiratory ullness but can be ascoiated with a stomach virus & also the mucus from the flu can cause nausea & vomitting & headaches etc.

All those that you mentioned is associated with flu, even though beingan upper respitory problem.

All I know is that when I have the flu, my respiratory functions (lol) are fine. But, I am dizzy, my muscles ache so badly that I cannot stand it and everytime I turn my head, I throw up. I, personally, have never had a sore throat or a cough when I had the flu. Just massive throwing up. I hate it. But, there are a lot of people who get the coughing and the sore throat. I don't know.