Inanimate agents such as bedding, toys, books, and surgical instruments can also transmit disease. These inanimate objects are collectively called fomites. Food and water are potential disease vehicles. Fomites can also be disease vehicles, but major epidemics originating from a single-vehicle source are typically traced to common sources such as food or water because food and water are shared commodities consumed in large amounts by everyone.
Epidemics
Major epidemics are usually classified as either common-source epidemics or host-to-host epidemics.
A common-source epidemic arises as the result of infection (or intoxication) of a large number of people from a contaminated common source such as food or water. Such epidemics are
often caused by a breakdown in the sanitation of a central food or water distribution system. Foodborne and waterborne common source epidemics are primarily intestinal diseases; the pathogen leaves the body in fecal material, contaminates food or water supplies due to improper sanitary procedures, and then enters the intestinal tract of the recipient during ingestion of the food or water. Waterborne and food borne diseases are generally controlled by public health measures.
A classic common-source epidemic is cholera. In 1855 the British physician John Snow showed that cholera spreads through drinking water. His studies correlating cholera incidence with water distribution systems in London demonstrated
that cholera is spread by fecal contamination of a water supply. The infectious agent, the bacterium Vibrio cholerae, was transmitted through consumption of the contaminated common-source vehicle, water.