Symptoms primarily depend on the age of the person and the strength of his or her immune system.
CMV may infect a healthy unborn baby while it is still in the womb. Roughly 5% of infants who get CMV this way have serious birth defects. These can include brain damage, growth failure, blindness, and other defects. This problem usually occurs when a pregnant mother gets a CMV infection for the first time during pregnancy.
When CMV happens in early childhood, it usually causes no symptoms at all. This is thought to be the most common form of CMV infection.
During the teenage and young adult years, infection with CMV can cause a syndrome called infectious mononucleosis, or "mono." Mono generally causes symptoms of sore throat, fatigue, fever, and swollen glands. These symptoms can last for weeks or even months. Most people recover without treatment.
CMV can cause serious problems in people with weakened immune systems. This problem is most common in people with AIDS or those taking drugs to suppress the immune system. People with widespread cancer or people who receive an organ transplant are commonly affected. Infection may be due to a first-time infection or, more often, a reactivated infection. People with AIDS often get an infection of the back of the eye, called the retina. This type of infection is called retinitis. This may cause problems with vision. In transplant and cancer patients, CMV usually is the cause of pneumonia or a gastrointestinal infection that causes diarrhea.