Quinine's target is the disease AGUE, which is a four-letter word, and MALARIA, which is a seven-letter word. AGUE is an old-fashioned term for a fever or chill, usually associated with MALARIA. MALARIA is a mosquito-borne infectious disease caused by a parasite that can cause severe fever, chills, and flu-like illness. Quinine is an alkaloid derived from the bark of the cinchona tree, which has been used to treat MALARIA since the 1600s.