The term FLU is an abbreviation for the infectious disease influenza, which is caused by a virus. The crossword solutions for this term are ASIAN (5 letters), BUG (3 letters), AGUE (4 letters), and GRIPPE (6 letters). ASIAN refers to the type A strain of the influenza virus, which is the most common and severe form of the virus. BUG is a slang term for a virus, and AGUE is an old-fashioned word for a fever or other symptoms of illness. GRIPPE is a French word for influenza, which is derived from the Latin word for 'INFLUENCE'.