I had flu getting on for four weeks ago - no official diagnosis but temp/chills/aches and pains/cough/fatigue so pretty sure that's what it was. I thought I'd recovered, apart from the cough, but now my temperature's up again and the cough's got worse. It seems too much of a coincidence that I could have got something else so soon. Do relapses happen with flu? I went back to work after a week, coughing away, would I have been.infectious?