When did people believed that just breathing the stench of an infected person would infect them?

During the Middle Ages, particularly around the 14th century during the Black Death, people believed that diseases could be transmitted through "miasma," or bad air. This theory held that foul odors from infected individuals or decaying matter could spread illness simply by being inhaled. This belief persisted for centuries until the development of germ theory in the 19th century, which established that diseases are caused by microorganisms rather than miasma.