When people got sick with fever and chills back in colonial times, they called their illness ague. Today most people would refer to ague as malaria.
Starting in the 13th century, feverish illness was named ague, from the Medieval Latin acuta, "sharp fever," and its root, meaning "sharp." The word began to refer specifically to malaria, an infectious disease spread by mosquitoes, as early as the late 14th century. Colonial doctors often attributed cases of ague to "bad air," and the illness reached epidemic levels several times. It was eliminated as a public health issue in the U.S. around 1950, although malaria is still a problem in other parts of the world.