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da Silva, Luiz Jacintho M.D.

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The Pediatric Infectious Disease Journal: December 1997 - Volume 16 - Issue 12 - p 1188
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To The Editors:

An important step in the search for the meaning of words was ignored in the article by Katz and Finberg.1 Words have different meanings according to time, place and language. A review of current dictionaries adds very little; etymology is the study of the development and origins of words.

According to The concise dictionary of English etymology,2 infest derives from the Latin infestare, to attack. Infection derives from infectus, also Latin, meaning to put in, stain, dye.

The Collins English dictionary3 also brings the same etymology cited above. The definition also clearly states a difference between both words:

  • infection: 1. invasion of the body by pathogenic organisms. 2. the resulting condition in the tissues. 3. an infectious disease. 4. the act of infecting or being infected. 5. an agent or influence that infects. 6. persuasion or corruption, as by ideas, perverse influences etc.
  • infest: 1. to inhabit or overrun in dangerously or unpleasantly large numbers. 2. (of parasites such as lice) to invade or live on or in (a host).

As we see there may not be an ironclad difference between both terms, but there is enough to understand clearly that they have distinct origins and different meanings. Infest conveys the idea of external attack upon something, very appropriate for ectoparasites; infection, on the other side, conveys the idea of an internal parasitism, attack may be included, but attack with penetration.

This seems to be sufficient evidence for editors to insist that infection and infestation not be used as synonyms, without having to convene an international consensus conference.

Luiz Jacintho da Silva, M.D.

Departado Clinica Medica; FCM, Unicamp; Campinas, Sao Paulo, Brazil

1. Katz M, Finberg L. Terms of mutualism. Pediatr Infect Dis J 1997;16:520-1.
2. Collins dictionary of the English language. London: William Collins & Son, 1982.
3. Skeat WW. The concise dictionary of English etymology. Hertfordshire, Wordsworth Editions, Ltd., 1993.

Infection; infestation

© Williams & Wilkins 1997. All Rights Reserved.