Cytomegalovirus, or CMV, is a virus commonly found in people of all ages. Most healthy people who have CMV do not have any symptoms and do not know they have the virus. When symptoms do occur, they may include fever, fatigue, sore throat, swollen glands, and sometimes a rash. However, CMV can cause more serious problems for people with weakened immune systems and for some babies who are born with the infection (known as congenital CMV).

In the United States, CMV infection is widespread. Nearly one in three children is infected with CMV by age five, and over half of adults have been infected by age 40. Around one in 200 babies is born with congenital CMV infection. CMV is the most common infectious cause of birth defects in the country.

CMV can be managed, and most healthy people recover without any treatment. For those who develop more serious illness, especially people with weakened immune systems or newborns with symptoms, antiviral medications may help control the infection and improve outcomes.

CMV is a type of herpesvirus. As with other types of herpesvirus (such as the varicella-zoster virus, which causes chickenpox and shingles), once a person is infected, the virus stays in the body for life, usually in a dormant, or inactive, state. Most people who have CMV do not experience any symptoms or only have mild symptoms, similar to a cold or flu. Most people never know if they have had the virus. However, CMV can sometimes become active again, especially if the immune system becomes weakened. When this happens, the virus can cause illness and infect different organs and tissues in the body.

Although CMV infection can occur at any age, it can be serious in newborns and people with weakened immune systems, as they are at higher risk for complications.

In healthy people, the immune system usually keeps CMV under control, so it does not cause harm. But in people with weakened immune systems—such as those who have received organ or stem cell transplants, are undergoing chemotherapy, or are living with HIV/AIDS—CMV can reactivate and spread, leading to more serious disease. In these cases, the virus can cause inflammation and damage to the eyes, lungs, liver, brain, and digestive tract. This may result in symptoms such as vision loss, pneumonia, hepatitis, or problems with the digestive system.

CMV can also infect babies before birth, a condition known as congenital CMV. Most babies with congenital CMV have no symptoms at birth. About 10% have signs at birth, such as jaundice, rash, low birth weight, enlarged liver or spleen, or small head size. About one in five babies with congenital CMV has birth defects or long-term issues, most often hearing loss. Some may have developmental delays or vision problems. Hearing loss can develop later, even in babies who had no symptoms at birth.

CMV is caused by infection with the cytomegalovirus. The virus spreads from person to person through direct contact with body fluids such as saliva, urine, blood, tears, semen, vaginal fluids, and breast milk. People can become infected by close contact with young children who are shedding the virus in urine or saliva, through sexual contact with someone who has an active infection, or by receiving an organ transplant or blood transfusion from an infected donor. CMV can be passed from mother to baby during pregnancy, birth, or breastfeeding.

In some cases, a person who has already had CMV can be infected again with a different strain of the virus.

Risk factors for cytomegalovirus include:

• Having a weakened immune system (such as from HIV/AIDS, organ or stem cell transplantation, chemotherapy, or immunosuppressive medications)
• Pregnancy
• Exposure to saliva and urine of young children who have CMV
• Receiving a blood transfusion or organ transplant from a CMV-infected donor
• Older age
• Living in crowded conditions
• Lower socioeconomic status
• Not washing hands after contact with urine or saliva

Pregnant women can pass CMV infection to their fetus, especially if they become infected or CMV reactivates during the first trimester of pregnancy.

Most people who become infected with CMV have no symptoms. However, some people with cytomegalovirus may experience cold- or flu-like symptoms. These may include:

• Fever
• Fatigue
• Sore throat
• Swollen glands
• Muscle aches
• Loss of appetite
• Rash
• Enlarged lymph nodes

Cytomegalovirus can infect different tissues and organ systems, mostly in people with compromised immune systems, such as after organ transplant or due to HIV/AIDS. In more severe cases, symptoms can include:

• Vision changes or vision loss
• Diarrhea
• Abdominal pain
• Weight loss
• Cough or shortness of breath
• Retinitis (inflammation of the retina, which can cause vision problems)
• Neurologic symptoms, such as confusion, seizure, or weakness

Newborns who are born with CMV may show the following symptoms:

• Rash
• Enlarged liver or spleen
• Jaundice (yellowing of the skin or eyes)
• Low birth weight
• Small head size (microcephaly)
• Hearing loss
• Seizures
• Damage to the retina
• Long-term health problems, such as hearing or vision loss, lack of coordination, or developmental delays.

To diagnose cytomegalovirus, your doctor will review your medical history, conduct a physical exam, and order one or more diagnostic tests.

Your doctor may ask you about your symptoms, recent illnesses, possible exposure to young children, and any risk factors such as recent organ transplantation, blood transfusion, or pregnancy. During the physical exam, your doctor may look for signs such as fever, swollen glands, rash, enlarged liver or spleen, or other symptoms related to affected organs.

Additional tests are typically necessary to make a diagnosis, including:

• Polymerase chain reaction (PCR) testing: This is the most common test for active disease and detects CMV DNA in blood, saliva, urine, or tissue samples. This is the standard test for accurate detection and is used for newborns.
• Serologic tests (antibody tests): Measure CMV-specific antibodies in the blood to detect current or past infection. These tests are most useful for assessing prior exposure or recent infection but are not reliable for diagnosing CMV in newborns.
• Tissue biopsy with histopathology or immunohistochemistry: Examines tissue samples for characteristic CMV-infected cells, especially in cases of organ involvement.

For newborns with symptoms, testing should be done within the first two to three weeks of life using urine samples to confirm congenital CMV infection. In the United States, some states perform targeted CMV testing for newborns who fail the hearing screening. Some states perform bloodspot screening for congenital CMV for all newborns. Otherwise, most babies are not routinely screened for CMV.

Pregnant women with no CMV symptoms are also not routinely tested for CMV infection because lab tests cannot predict if the baby will get CMV or if they will have any long-term health problems as a result.

There is no cure for CMV, but most healthy people recover without any specific treatment. For people with weakened immune systems, pregnant women, or newborns who develop symptoms, or those with severe disease, antiviral medications and supportive care may be recommended to control the infection and reduce complications.

Main treatments for CMV include:

• Observation and supportive care: Most healthy people with mild symptoms do not need treatment, and symptoms usually resolve on their own with rest and fluids. Over-the-counter painkillers and gargling with warm salt-water can soothe aches and pains as well as sore throat.
• Antiviral medications: These drugs, such as ganciclovir, valganciclovir, foscarnet, cidofovir, maribavir, and letermovir, help slow the growth of the virus. They are used for people with weakened immune systems, newborns with symptoms, or people with severe disease. Antivirals can reduce the severity of symptoms and help prevent complications, but they do not cure the infection. Antivirals may be used to help prevent CMV in people receiving an organ transplant from a donor who tests positive for CMV.
• Immune globulin therapy: In some cases, especially for transplant recipients, immune globulin (antibody) therapy may be used to help the body fight the virus.
• Monitoring and prevention: In high-risk patients, such as organ or stem cell transplant recipients, doctors may use antiviral medications to prevent CMV infection or monitor for early signs of the virus and start treatment before symptoms develop.

Treatment plans are tailored to each person’s needs, and doctors carefully monitor for side effects of antiviral medications, which can include effects on the kidneys, bone marrow, or other organs.

People with CMV may be at increased risk for certain complications, including:

• Hearing loss: Babies with congenital CMV may have hearing loss at birth or develop it later in childhood.
• Developmental delays: Babies with congenital CMV may experience delays in motor skills, speech, or learning.
• Seizures: Some infants with congenital CMV may have seizures.
• Vision loss or blindness: CMV can cause retinitis, an infection of the retina, which may lead to vision problems or blindness, particularly in people with weakened immune systems.
• Encephalitis: Inflammation of the brain, which can cause confusion, weakness, or other neurological symptoms.
• Pneumonia: Infection of the lungs, which can be severe in people with weakened immune systems.
• Hepatitis: Inflammation of the liver, which may cause jaundice or liver dysfunction.
• Colitis: Inflammation of the colon, leading to diarrhea, abdominal pain, and sometimes bleeding.
• Gastrointestinal ulcers or bleeding: CMV can cause ulcers in the digestive tract, which may result in pain or bleeding.
• Bone marrow suppression: Reduced production of blood cells, which can lead to anemia, low white blood cell counts, or low platelets.
• Graft rejection or dysfunction: In people who have received organ or stem cell transplants, CMV infection can increase the risk of rejection or loss of the transplanted organ.
• Secondary infections: CMV can weaken the immune system, making it easier to get other infections.
• Death: In severe cases, especially in people with weakened immune systems or in newborns with serious disease, CMV infection can be life-threatening.

The outlook for people with CMV can vary widely depending on factors such as age, overall health, immune system strength, and whether the infection is acquired before birth or later in life. Most healthy people who get CMV have no symptoms or only mild illness, and they recover fully without any long-term effects. In these cases, CMV does not usually cause lasting harm.

For people with weakened immune systems, such as those who have received organ or stem cell transplants, are undergoing chemotherapy, or are living with HIV/AIDS, CMV can cause more serious illness and complications. Babies born with congenital CMV who have symptoms at birth are at higher risk for long-term problems, such as hearing loss, developmental delays, or vision loss.

With early detection and appropriate treatment, many people—including those at higher risk—can manage the infection and reduce the risk of severe complications. Regular monitoring and advances in antiviral therapies have improved outcomes for people with CMV, especially in high-risk groups.

“With the new congenital CMV screening program for all babies in the state of Connecticut, the Department of Pediatrics at Yale Medicine has developed a comprehensive, multidisciplinary program to evaluate and care for newborns with congenital CMV,” says Thomas Murray, MD, PhD, a pediatric infectious disease specialist at Yale Medicine. “This includes an initial evaluation by a pediatric infectious disease specialist regarding the need for antiviral medication and additional testing. We also offer careful long-term follow up with audiologists and pediatricians with expertise in infant and child development to ensure babies with congenital CMV receive the highest standard of care beyond the newborn period.”