Contagious disease

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Contagious disease
This clinic uses negative room pressure to prevent disease transmission
SpecialtyInfectious diseases

A contagious disease is an infection that can readily spread to a person from an infected person, contaminated surface or object, or by ingesting contaminated food or water.[1]

Public health response

Most epidemics are caused by contagious diseases, with occasional exceptions, such as yellow fever. The spread of non-contagious communicable diseases is changed either very little or not at all by medical isolation of ill persons or medical quarantine for exposed persons. Thus, a "contagious disease" is sometimes defined in practical terms, as a disease for which isolation or quarantine are useful public health responses.[2][failed verification]

Some locations are better suited for the research into the contagious pathogens due to the reduced risk of transmission afforded by a remote or isolated location.

Negative room pressure is a technique in health care facilities based on aerobiological designs.

Historical meaning

Originally, the term referred to a contagion (a derivative of 'contact') or disease transmissible only by direct physical contact. In the modern-day, the term has sometimes been broadened to encompass any communicable or infectious disease. Often the word can only be understood in context, where it is used to emphasize very infectious, easily transmitted, or especially severe communicable diseases.

A disease is often known to be contagious before medical science discovers its causative agent. Koch's postulates, which were published at the end of the 19th century, were the standard for the next 100 years or more, especially with diseases caused by bacteria. Microbial pathogenesis attempts to account for diseases caused by a virus.

The disease itself can also be called a contagion.

In 1849, John Snow first proposed that cholera was a contagious disease.

See also


  1. "Merriam-Webster dictionary definition of contagious disease". Archived from the original on 2005-03-31. Retrieved 2009-11-27.
  2. A primer from the CDC on quarantine and its uses against contagious disease spread Archived 2012-03-02 at the Wayback Machine Accessed Nov. 27, 2009.