Cytomegalovirus (CMV) Infection

How CMV spreads

CMV passes through close contact with body fluids:

• saliva (kissing, sharing cups, utensils and toothbrushes)
• urine and diapers of young children, who can shed the virus for months to years
• sexual contact
• breast milk
• organ and stem cell transplants, and rarely blood transfusions
• from mother to baby during pregnancy

After the first infection, CMV stays dormant (latent) in the body and can reactivate, especially if the immune system weakens. People can also be reinfected with a different strain.

CMV in healthy children and adults

Most infections cause no symptoms. When they do, they resemble infectious mononucleosis, which is usually caused by the related Epstein-Barr virus:

• fever lasting days to weeks
• fatigue
• swollen lymph nodes
• sore throat (usually milder than with EBV mono)
• muscle aches
• mildly abnormal liver tests

CMV causes about 1 in 10 cases of mono-like illness. Recovery is usually complete without treatment.

Congenital CMV

When a pregnant person has a first (primary) CMV infection, the virus passes to the baby in about a third of cases. Reinfection or reactivation can also infect the baby, though less often. Infection early in pregnancy causes more severe effects.

Effects on babies

About 1 in 200 babies is born with CMV, and about 1 in 5 of them will have long-term health problems:

• hearing loss, which may be present at birth or develop over the first years of life; often in one ear at first
• small head size (microcephaly), brain calcifications
• vision problems
• developmental delay, cerebral palsy, seizures
• at birth: low birth weight, jaundice, enlarged liver and spleen, small purple skin spots, pneumonia

Most infected babies look healthy at birth. That is why testing is important when a baby fails the hearing screen. See congenital infections for other infections that affect babies.

CMV in people with weakened immunity

People with HIV with a low CD4 count, organ or stem cell transplant recipients, and those on strong immune-suppressing drugs can develop serious CMV disease:

• retinitis (see chorioretinitis): floaters, blind spots and vision loss that can lead to blindness
• colitis and esophagitis: diarrhea, bleeding, abdominal pain, painful swallowing
• pneumonitis: cough and breathlessness
• hepatitis, encephalitis
• transplant rejection and increased infections

Transplant centers monitor CMV levels in the blood and use preventive antivirals.

Diagnosis

• Blood antibody tests (IgG and IgM): show past or recent infection; an IgG avidity test helps date infection in pregnancy.
• PCR testing: detects the virus in blood, urine, saliva or tissue. For newborns, a urine or saliva PCR within the first 3 weeks of life confirms congenital CMV; after that, it cannot distinguish congenital from later infection.
• Viral load monitoring in transplant patients.
• Eye exam for retinitis; biopsy for gut or lung disease.
• Prenatal tests: ultrasound for signs of fetal infection and amniocentesis for CMV PCR.

Treatment

• Healthy people: no antiviral treatment is usually needed; rest, fluids and fever relief with acetaminophen (paracetamol) or ibuprofen, following the label dose.
• Babies with symptomatic congenital CMV: oral valganciclovir for 6 months, started within the first month of life, can improve hearing and developmental outcomes.
• Weakened immunity: ganciclovir, valganciclovir, foscarnet, cidofovir, or newer drugs such as letermovir (for prevention) and maribavir (for resistant infection).
• Pregnancy: there is no proven treatment to prevent transmission; research continues on antivirals such as high-dose valacyclovir in early pregnancy.

Prevention

There is no vaccine yet. To reduce the risk in pregnancy:

• wash hands with soap and water for 15 to 20 seconds after changing diapers, feeding a young child, wiping noses or handling toys
• do not share food, drinks, utensils or toothbrushes with young children
• kiss children on the forehead or cheek rather than the mouth
• clean toys and surfaces that touch children's saliva or urine

Transplant recipients receive preventive antivirals or regular monitoring. CMV-safe blood products are used for at-risk patients.

Frequently asked questions

What are the symptoms of CMV in adults?

Most healthy adults have no symptoms. Some develop a mono-like illness with fever, fatigue, swollen glands, sore throat and muscle aches, lasting a few weeks. People with weakened immune systems can develop serious eye, lung, gut or brain infections.

How is CMV spread?

CMV spreads through close contact with saliva, urine, tears, breast milk and genital fluids, as well as transplants and, rarely, transfusions. Young children are a common source, so good hand hygiene around their saliva and diapers helps prevent infection.

Is CMV dangerous during pregnancy?

It can be. A CMV infection during pregnancy, especially a first infection in early pregnancy, can pass to the baby and cause hearing loss, vision problems and developmental delays. Hand hygiene and avoiding young children's saliva reduce the risk.

Can CMV be cured?

No. Once infected, CMV stays in the body for life, usually dormant and harmless. Antiviral medicines control active infection in newborns and people with weakened immunity but do not eliminate the virus.

What is congenital CMV?

Congenital CMV is infection passed from mother to baby before birth. It affects about 1 in 200 babies. Most look healthy at birth, but some develop hearing loss, vision problems or developmental delay, which is why early testing and follow-up matter.