Contagious disease

Contagious disease

A contagious disease is a subset category of infectious diseases (or communicable diseases), which are easily transmitted by physical contact (hence the name-origin) with the person suffering the disease, or by their secretions or objects touched by them.[1]

The non-contagious category of infectious/communicable diseases usually require a special mode of transmission between hosts. These include need for intermediate vector species (such as a mosquito for yellow fever), direct blood contact (such as transfusion or needle-sharing), or sexual contact (examples are AIDS and hepatitis B).

The boundary between contagious and non-contagious infectious diseases is not perfectly drawn, as illustrated classically by tuberculosis, which is clearly transmissible from person to person, but was not classically considered a contagious disease. In the present day, most sexually transmitted diseases are considered contagious, but only some of them are subject to medical isolation.

Historical meaning

Originally, the term referred to a contagion (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 emphasise very infectious, easily transmitted, or especially severe communicable disease.[2]


Usually, epidemics are caused only by contagious diseases, but occasional exceptions occur, such as with black plague. This is because epidemics may also be regarded in terms of proportion of people infected with a transmissible disease.

Because of the nature of non-contagious communicable diseases, such as yellow fever or filariasis, their spread is little affected or not affected by medical isolation (for ill persons) or medical quarantine (for exposed persons). Thus, a "contagious disease" is sometimes defined in practical terms of whether isolation or quarantine make sense as a public health response.[3]


  1. ^ Merriam-Webster dictionary definition of contagious disease. Accessed Nov. 27, 2009
  2. ^ Definition from nursing encyclopedia.
  3. ^ [1] A primer from the CDC on quarantine and its uses against contagious disease spread. Accessed Nov. 27, 2009.

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Look at other dictionaries:

  • Contagious disease — Con*ta gious dis*ease (Med.) A disease communicable by contact with a patient suffering from it, or with some secretion of, or object touched by, such a patient. Most such diseases have already been proved to be germ diseases, and their… …   The Collaborative International Dictionary of English

  • contagious disease — n an infectious disease communicable by contact with one who has it, with a bodily discharge of such a patient, or with an object touched by such a patient or by bodily discharges compare COMMUNICABLE DISEASE * * * originally, a disease… …   Medical dictionary

  • contagious disease — užkrečiamoji liga statusas T sritis ekologija ir aplinkotyra apibrėžtis Liga, kurią sukelia į organizmą įsiskverbę patogeniniai mikrobai (bakterijos, virusai, grybai, pirmuonys). Plinta pavieniais susirgimais arba masiniais protrūkiais,… …   Ekologijos terminų aiškinamasis žodynas

  • contagious disease — kontaginė liga statusas T sritis apsauga nuo naikinimo priemonių apibrėžtis Užkrečiamoji liga, kuri gali plisti nuo užkrėstųjų sveikiesiems pro odą ir gleivines (kontaktiniu būdu). Lengviausiai perduodamas maras, raupai, cholera, dėmėtoji šiltinė …   Apsaugos nuo naikinimo priemonių enciklopedinis žodynas

  • contagious disease — noun any disease easily transmitted by contact • Syn: ↑contagion • Derivationally related forms: ↑contagious (for: ↑contagion) • Hypernyms: ↑communicable disease …   Useful english dictionary

  • contagious disease — A disease communicable by contact, or by bodily exhalation. Grayson v Lynch 163 US 468, 477, 41 L Ed 230, 233, 16 S Ct 1064. See infectious disease …   Ballentine's law dictionary

  • contagious disease — communicable disease …   The new mediacal dictionary

  • contagious disease — illness that can be spread by contact …   English contemporary dictionary

  • contagious disease — One capable of being transmitted by mediate or immediate contact …   Black's law dictionary

  • contagious disease — One capable of being transmitted by mediate or immediate contact …   Black's law dictionary

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