Common ailment (3)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">common ailment</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for flu that I've seen before include "Common annual illness" , "Common disease" , "Winter disease, awfully avian" , "Common infection" , "Infection reduced" .)
(Other definitions for influenza that I've seen before include "Nasty viral disease, usually of winter" , "Viral infection" , "Common viral disease" , "respiratory ailment" , "Respiratory complaint" .)