What is cytomegalovirus?

Cytomegalovirus (CMV) is a common virus that can infect almost anyone. Most people don’t know they have CMV because it rarely causes symptoms. However, if you’re pregnant or have a weakened immune system, CMV is cause for concern.

Once infected with CMV, your body retains the virus for life. However, CMV usually remains dormant if you’re healthy.

CMV spreads from person to person through body fluids, such as blood, saliva, urine, semen and breast milk. CMV spread through breast milk usually doesn’t make the baby sick. However, if you are pregnant and develop an active infection, you can pass the virus to your baby.

There’s no cure for CMV, but drugs can help treat newborns and people with weak immune systems.


Cytomegalovirus is related to the viruses that cause chickenpox, herpes simplex and mononucleosis. Once you’re infected with CMV, the virus remains with you for life, but it’s not always active. CMV may cycle through periods during which it lies dormant and then reactivates. If you’re healthy, it mainly stays dormant. You can pass the virus to others during reactivation.

Transmission of the virus occurs through exposure to body fluids — including blood, urine, saliva, breast milk, tears, semen and vaginal fluids — not by casual contact.

The virus can spread in a number of ways:

  • Touching your eyes or the inside of your nose or mouth after coming into contact with the body fluids of an infected person. This is the most common way CMV is spread because it’s absorbed through the mucous membranes.
  • Through sexual contact with an infected person.
  • Through the breast milk of an infected mother.
  • Through organ transplantation or blood transfusions.
  • Through the placenta, from an infected mother to her unborn child, or during birth.

Risk factors

CMV is a widespread and common virus that can infect almost anyone. But healthy children and adults who contract the infection usually have few if any symptoms, so CMV often goes undiagnosed.


In the rare cases in which CMV causes a healthy person to become very sick, the infection may cause the following complications:

CMV mononucleosis
This syndrome resembles infectious mononucleosis, but the Epstein-Barr virus (EBV) causes classic mononucleosis. If you have signs and symptoms that resemble mononucleosis — a sore throat, swollen glands and tonsils, fatigue, and nausea — your doctor will test you for the antibody your body makes to fight off EBV. If it’s absent, there’s a chance CMV is causing your symptoms
Intestinal complications
CMV infection in your intestines can result in diarrhea, fever and abdominal pain; inflammation of your colon; and blood in your stool.
Liver complications
CMV can cause abnormal functioning of your liver and an unexplained fever.
Nervous system complications
A variety of neurological complications have been reported as a result of CMV infection in the nervous system. These may include inflammation of your brain (encephalitis).
Lung complications
CMV can cause inflammation of your lung tissue (pneumonitis).