Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


noun cy·to·meg·a·lo·vi·rus \ˌsī-tə-ˌme-gə-lō-ˈvī-rəs\

Definition of cytomegalovirus

  1. :  a herpesvirus (species Human herpesvirus 5 of the genus Cytomegalovirus) that causes cellular enlargement and formation of eosinophilic inclusion bodies especially in the nucleus and acts as an opportunistic infectious agent in immunosuppressed conditions (as AIDS)

Origin and Etymology of cytomegalovirus

New Latin, from cytomegalia + -o- + virus

First Known Use: 1963

Medical Dictionary


noun cy·to·meg·a·lo·vi·rus \ˌsīt-ə-ˌmeg-ə-lō-ˈvī-rəs\

Medical Definition of cytomegalovirus

  1. 1:  a herpesvirus (species Human herpesvirus 5 of the genus Cytomegalovirus) that in healthy individuals causes an infection that is asymptomatic or is accompanied by mild symptoms (as fever or fatigue) but in immunocompromised individuals and newborns may cause an infection marked by serious, sometimes life-threatening symptoms (as pneumonia, hepatitis, retinitis, brain inflammation, or seizures) Cytomegalovirus is transmitted chiefly in infected body fluids and secretions (such as urine or saliva) and causes enlargement of infected cells and formation of inclusion bodies. <Human cytomegalovirus (HCMV), a DNA herpesvirus with more than 200 genes, is a giant among viruses.—Bernard Roizman, Science, 30 June 2000> <Her vision was failing at that point from CMV, cytomegalovirus, a common and usually harmless bug that can turn vicious in AIDS cases.—Peter Goldman and Lucille Beachy, Newsweek, 21 July 1986> <Ganciclovir and foscarnet can be used to treat respiratory tract infections caused by cytomegalovirus in immunocompromised adults.—Harvey B. Simon, Scientific American Medicine, September 1994>

  2. 2:  infection with or disease caused by the cytomegalovirus <Many of recent patients had also been treated for viral inflections such as herpes, cytomegalovirus and hepatitis B, as well as parasitic infections such as amoebiasis and giardiasis, the CDC said.—The Springfield (Massachusetts) Morning Union, 29 Aug. 1981> <Cytomegalovirus retinitis can cause retinal detachment and these patients may complain of floaters, flashing lights, or loss of vision, although the onset of vision loss in these patients tends to occur more suddenly and can be described as a “curtain coming down over the eye.”—Scott M. Whitcup, The Journal of the American Medical Association, 10 Jan. 1996>—abbreviation CMV

Learn More about cytomegalovirus

Seen and Heard

What made you want to look up cytomegalovirus? Please tell us where you read or heard it (including the quote, if possible).


a very small amount

Get Word of the Day daily email!


Take a 3-minute break and test your skills!


Which is the correct spelling?

accomodate acommadate acommodate accommodate
Name That Thing

Test your visual vocabulary with our 10-question challenge!


Test Your Knowledge - and learn some interesting things along the way.