Cytomegalovirus (CMV) is a virus that commonly causes infection. CMV infection may cause flu-like illness or even no symptoms. Most adults and many children have been around someone with CMV. After a person has had a CMV infection, the virus becomes non-active in the body. It can reactivate months or years later. Reactivation of the virus most often happens when a person's immune system is weakened or suppressed.

People most likely to have a weakened immune system include those:

  • With acquired immune deficiency syndrome (AIDS)
  • Treated with chemotherapy, radiation therapy or steroid therapy
  • Who have received an organ or bone marrow transplant