Skip to main content

Health library

Back to health library

What is cytomegalovirus (CMV)?

Cytomegalovirus lives inside almost all of us and usually causes no trouble. But for people with weakened immune systems, the virus can be fatal.

More than half of adults are infected with CMV by 40 years of age, according to the Centers for Disease Control and Prevention (CDC). It spreads through almost every human body fluid, including saliva, urine, semen and blood.

Once CMV enters the body it never leaves. In healthy adults, the virus usually produces no symptoms or illness.

In some people the virus activates occasionally. While activated, it produces mild symptoms, including fever, fatigue and swollen lymph glands, before returning to dormancy.

CMV can be a far more serious problem for people with weakened immune systems. People being treated for cancer or who have had a recent organ transplant can get seriously ill from CMV. HIV-infected people with advanced immunosuppression are also at risk. In these cases, CMV can cause pneumonia, hepatitis, encephalitis, colitis and retinitis. The illness may be fatal.

If a woman is infected early in her pregnancy, the virus can cause birth defects. The child may also develop hearing, vision or cognitive problems later in life.

CDC and March of Dimes suggest these measures for avoiding CMV infection during pregnancy:

  • Wash your hands often with soap and water, especially after changing diapers.
  • Do not kiss young children on the mouth or cheek. Kiss them on top of the head or give them a hug.
  • Don't share food, drinks or eating utensils with young children.

All childcare providers should wash their hands frequently, as CMV often spreads in this setting. Providers typically come in contact with urine and saliva and can spread the virus to other children.

Most people will never be treated for CMV because they don't get sick from it. However, those with weakened immune systems may be given antiviral medications. They are not recommended in all cases.

Reviewed 10/09/2022

Related stories