The prevailing thought in Victorian healthcare concerning the transmission of contagious diseases was the miasma theory, which held that most communicable diseases were caused by the inhalation of contaminated air. This contamination could take the form of the odour of rotting corpses or sewage, but also rotting vegetation, or the exhaled breath of someone already diseased. Miasma was believed by most to be the vector of transmission of cholera, which was on the rise in 19th-century Europe. The disease was deeply feared by all, because of the speed with which it could spread, and its high fatality rates.