Causes

CMV is related to the viruses that cause chickenpox, herpes simplex and mononucleosis. CMV may cycle through periods when it lies dormant and then reactivates. If you're healthy, CMV mainly stays dormant.

When the virus is active in your body, you can pass the virus to other people. The virus is spread through body fluids — including blood, urine, saliva, breast milk, tears, semen and vaginal fluids. Casual contact doesn't transmit CMV.

Ways the virus can be transmitted include:

• Touching your eyes or the inside of your nose or mouth after coming into contact with the body fluids of an infected person.
• Sexual contact with an infected person.
• The breast milk of an infected mother.
• Organ, bone marrow or stem cell transplantation or blood transfusions.
• Birth. An infected mother can pass the virus to her baby before or during birth. The risk of transmitting the virus to your baby is higher if you become infected for the first time during pregnancy.