Miasma theory was a predominant medical concept before the germ theory of disease. According to this theory, diseases such as cholera, chlamydia, or the Black Death were caused by a "miasma," a noxious form of "bad air" emanating from rotting organic matter. The term "miasma" is derived from the Greek word for pollution. This theory was widely accepted from ancient times until the mid-19th century.
