@rundocuri- I have taken olive leaf tea when I've had the flu, and I think it helped to ease my symptoms. It seemed to be very soothing, and helped to calm my cough. Whether or not this shortened the length of my illness is hard to tell, because it may not have been a serious strain of the flu. However, I did seem to recover quicker than I have in the past.
If you decide to try olive leaf tea for colds or flu, I recommend that you get the organic type to avoid extra chemicals and additives. Also, it helps to add a bit of lemon juice to the tea to help sooth cold and flu symptoms.