Roughly half the adult population in the United States has been infected with cytomegalovirus, a herpesvirus that most people carry without ever knowing it. National survey data from 1999 to 2004 put the age-adjusted seroprevalence at about 50%, though more recent modeling suggests the figure climbs steadily with age and varies sharply across demographic groups. For the vast majority of healthy adults, CMV causes no symptoms at all. The virus matters most for pregnant women, newborns, and anyone whose immune system is suppressed, where it can cause serious and sometimes permanent harm.
How Many Americans Carry CMV
The best nationwide snapshot comes from the National Health and Nutrition Examination Surveys (NHANES). An analysis of the 1988–1994 survey cycle found that about 59% of people aged six and older tested positive for CMV antibodies, meaning they had been infected at some point in their lives.1Clinical Infectious Diseases. Seroprevalence of Cytomegalovirus Infection in the United States, 1988–1994 By the 1999–2004 cycle, the overall age-adjusted figure had dipped to about 50%.2Clinical Infectious Diseases. Cytomegalovirus Seroprevalence in the United States: The National Health and Nutrition Examination Surveys, 1988–2004 Whether that drop reflects genuine changes in transmission patterns or shifts in survey methodology is still debated, but the ballpark figure of one in two adults has remained the working estimate for years.
Seroprevalence increases steadily with age. In the 1988–1994 data, about 36% of children aged 6 to 11 were seropositive, while over 90% of adults aged 80 and older carried the virus.1Clinical Infectious Diseases. Seroprevalence of Cytomegalovirus Infection in the United States, 1988–1994 This gradient makes sense given how the virus spreads: the longer you live, the more opportunities you have to encounter it through close contact, sexual activity, or caregiving. More recent modeling of both US and Canadian data shows the climb in real time. At ages 18 to 19, modeled seroprevalence was roughly 49% in US women and 42% in US men. By ages 38 to 39, those numbers rose to about 62% and 50%, respectively.3PubMed. Estimated cytomegalovirus seroprevalence in the general population of the United States and Canada
Who Is More Likely to Carry It
CMV seroprevalence is not evenly distributed across the US population. Several factors push the numbers substantially higher or lower for different groups.
Women consistently test positive at higher rates than men across all age brackets.3PubMed. Estimated cytomegalovirus seroprevalence in the general population of the United States and Canada The gap is likely driven by women’s greater exposure to young children, who are prolific shedders of the virus. Childcare workers, mothers of toddlers, and anyone regularly handling diapers or wiping noses faces more opportunities for contact with CMV-laden saliva and urine.
Race and ethnicity mark some of the starkest differences. In the 1988–1994 NHANES data, seroprevalence was about 51% in non-Hispanic white participants, about 76% in non-Hispanic Black participants, and roughly 82% in Mexican American participants. Those gaps persisted even after controlling for income, education, household size, and other socioeconomic factors.1Clinical Infectious Diseases. Seroprevalence of Cytomegalovirus Infection in the United States, 1988–1994 The later 1999–2004 survey echoed the pattern, with seroprevalence higher among non-Hispanic Black and Mexican American children compared to non-Hispanic white children, and the gap widening through adulthood.2Clinical Infectious Diseases. Cytomegalovirus Seroprevalence in the United States: The National Health and Nutrition Examination Surveys, 1988–2004
Low household income, crowded living conditions, lower educational attainment, and being born outside the United States all independently raise the odds of testing positive.2Clinical Infectious Diseases. Cytomegalovirus Seroprevalence in the United States: The National Health and Nutrition Examination Surveys, 1988–2004 These disparities show up early in life and persist into middle age, meaning that the burden of congenital CMV and its downstream consequences also falls unevenly.4PubMed Central. Socioeconomic disparities in the seroprevalence of cytomegalovirus infection in the US population: NHANES III
How CMV Spreads
CMV travels in bodily fluids: saliva, urine, blood, breast milk, semen, and cervical secretions. In practical terms, the most common transmission routes are close contact with young children, sexual contact, organ transplantation, and blood transfusion. For most adults, the single biggest source of exposure is a toddler.
Young children who pick up CMV in daycare can shed the virus in their saliva and urine for months or even years. Research looking at surfaces inside homes with young children found that saliva-associated samples were more often CMV-positive and carried higher viral loads than urine-associated samples, and the heavier a child’s viral shedding, the more household surfaces tested positive.5PubMed Central. CMV on surfaces in homes with young children: results of PCR and viral culture testing This is why shared cups, pacifiers, and food are such efficient conduits. Molecular tracking studies have confirmed frequent CMV transmission among children in daycare settings, from those children to their parents, and from children to their caretakers.6PubMed. Molecular epidemiology of cytomegalovirus: viral transmission among children attending a day care center, their parents, and caretakers
One less-discussed route involves breast milk. For full-term, healthy newborns, breast-milk transmission is generally harmless. Premature, very-low-birthweight infants are another story: in babies weighing under about 1,500 grams, breast-milk-acquired CMV can trigger a severe sepsis-like syndrome with a range of organ involvement.7PubMed Central. Impact of breast milk-acquired cytomegalovirus infection in premature infants: Pathogenesis, prevention, and clinical consequences Neonatal units have to balance the well-documented benefits of breast milk against this risk, sometimes pasteurizing donor milk to inactivate the virus.8PubMed Central. How to Provide Breast Milk for the Preterm Infant and Avoid Symptomatic Cytomegalovirus Infection with Possible Long-Term Sequelae
What Happens After Infection
Once you are infected, CMV never leaves your body. The virus establishes lifelong latency in certain immune cells, particularly myeloid progenitor cells and monocytes. It stays quiet by actively suppressing the immune system’s ability to detect it, blocking antigen presentation, dampening natural killer cell surveillance, and preventing the infected cells from self-destructing.9PubMed Central. The Immunoregulatory Mechanisms of Human Cytomegalovirus from Primary Infection to Reactivation For people with a healthy immune system, this latent state causes no illness. The immune system keeps the virus in check indefinitely, even though it cannot eliminate it.
When CMV does cause noticeable illness in otherwise healthy adults, it usually looks like a mononucleosis syndrome: prolonged fever, fatigue, and muscle aches, but typically without the sore throat and swollen lymph nodes that characterize Epstein-Barr mononucleosis. Research from a tropical hospital setting found that CMV mononucleosis tended to appear in older adults, with a median age around 34, and featured a notably longer duration of fever, roughly two weeks compared to five days for Epstein-Barr cases.10PubMed Central. Comparative Clinical Characteristics of Cytomegalovirus and Epstein-Barr Virus Mononucleosis in Immunocompetent Hosts: Experience from a Tropical Setting This “CMV mono” can occasionally produce skin rashes and other complications, though these are relatively uncommon in people with healthy immune systems.11PubMed. Current understanding of cytomegalovirus infection in immunocompetent individuals
CMV in Pregnancy and Congenital Infection
The reason public health experts worry about CMV is what happens when the virus crosses the placenta. Congenital CMV is the most common congenital viral infection in the United States, affecting an estimated 4.6 to 4.7 out of every 1,000 live births nationally, with state-level rates ranging from about 3.9 to 6.5 per 1,000 between 2018 and 2022.12PubMed Central. Updated National and State-Specific Prevalence of Congenital Cytomegalovirus Infection, United States, 2018-2022 A separate modeling analysis estimated that about 12,300 infants were born with congenital CMV resulting from a first-time maternal infection in 2022 alone.13PubMed Central. Estimating the Prevalence of Congenital Cytomegalovirus Infection due to Primary Maternal Infection in the United States: A Probabilistic Risk Assessment Model
The risk of transmission to the fetus is much higher when a woman catches CMV for the first time during pregnancy, compared to when she already carries the virus and it reactivates. An Israeli study found that the risk of passing the virus to the fetus was roughly 1.8 times higher in primary infections than in non-primary infections.14PubMed Central. Primary versus nonprimary cytomegalovirus infection during pregnancy, Israel One European study even found that no women with non-primary infection transmitted CMV to their fetus in their cohort, though the confidence interval leaves open a small possibility.15PubMed. Human cytomegalovirus non-primary infection during pregnancy: antibody response, risk factors and newborn outcome This is a nuance that matters: women who were already seropositive before pregnancy have substantially lower transmission risk, though they are not fully protected.
What Congenital CMV Does to Children
Most babies born with congenital CMV have no obvious symptoms at birth. But even among apparently healthy infected newborns, a significant number develop problems later, especially hearing loss. CMV is the leading non-genetic cause of sensorineural hearing loss in children, contributing to roughly a quarter of childhood hearing loss by age four.16PubMed Central. CMV-induced Hearing Loss
The tricky part is that CMV-related hearing loss can be delayed, progressive, or fluctuating. A child can pass the newborn hearing screen and still develop hearing loss months or years later. In one cohort of children with confirmed congenital CMV, 75% had been diagnosed with sensorineural hearing loss by the time of the study. The average age of detection was 13 months, and over half of those children experienced further deterioration, with significant decline in hearing at an average age of about 41 months.17PubMed Central. Congenital Cytomegalovirus-Associated Sensorineural Hearing Loss in Children: Identification Following Universal Newborn Hearing Screening, Effect of Antiviral Treatment, and Long-Term Hearing Outcomes This means a single hearing test at birth is not enough; ongoing monitoring through at least age five or six is recommended for children known to have congenital CMV.16PubMed Central. CMV-induced Hearing Loss
Screening Newborns for CMV
Identifying congenital CMV early is critical because treatment within the first month of life can make a real difference in outcomes. The standard screening method is a saliva-based PCR test within the first few weeks of life. A large study of over 23,000 infants found an overall congenital CMV prevalence of about 3.7 per 1,000 live births. Saliva PCR caught about 93% of confirmed cases. Dried blood spot testing, which uses the heel-prick blood sample collected from nearly every newborn, was less sensitive at about 72–79% depending on the laboratory, but it picked up 81–91% of babies who went on to develop symptomatic disease.18JAMA Network Open. Dried Blood Spot PCR for Detection of Congenital Cytomegalovirus Infection and Disease
A growing number of US states have begun mandating or piloting universal newborn CMV screening, but it is not yet standard nationwide. The gap between how common congenital CMV is and how rarely parents have heard of it is striking. A systematic review of studies from multiple countries found that pregnant women’s awareness of CMV was generally low to moderate.19PubMed. Congenital cytomegalovirus infection: do pregnant women and healthcare providers know enough? A systematic review In a Swiss study, only about 39% of pregnant women had even heard of CMV, compared to over 95% awareness of HIV and hepatitis B, even though CMV infects far more newborns than either of those viruses.20PubMed Central. Awareness of Cytomegalovirus Infection among Pregnant Women in Geneva, Switzerland: A Cross-sectional Study
CMV in Transplant and HIV Patients
For people with suppressed immune systems, CMV is a different disease entirely. In organ transplant recipients, CMV is one of the most common infectious complications. The highest-risk scenario is when a CMV-positive donor organ goes to a CMV-negative recipient, because the recipient has no pre-existing immune response to the virus at all.21PubMed Central. Cytomegalovirus infection in transplant recipients Adding certain immune-suppressing drugs makes matters worse: patients treated with anti-lymphocyte antibodies for organ rejection develop CMV disease at three to four times the rate of those not receiving such therapy.22American Journal of Transplantation. American Society of Transplantation guidelines on cytomegalovirus infection in solid organ transplantation
In people living with HIV, CMV becomes a serious threat when CD4 counts fall extremely low. CMV retinitis, which destroys the retina and can cause blindness, typically develops once the CD4 count drops below about 50 cells per cubic millimeter.23PubMed Central. Cytomegalovirus retinitis associated with high CD4 counts and DHEA abuse In countries with limited access to antiretroviral therapy, CMV retinitis remains a leading cause of blindness among AIDS patients and has even been shown to increase mortality risk independently.24PubMed Central. Risk factors for CMV retinitis among individuals with HIV and low CD4 count in northern Thailand: importance of access to healthcare Widespread antiretroviral access in the US has dramatically reduced this complication, but it has not eliminated it.
Prevention Through Hygiene
No approved CMV vaccine exists yet, so prevention currently rests on behavioral measures, primarily good hand hygiene. The advice is straightforward: wash your hands thoroughly after changing diapers, avoid sharing utensils and cups with young children, and do not kiss toddlers on or near the mouth. These recommendations are especially important for pregnant women who have not already been infected.
Systematic reviews of hygiene-based interventions show that educating pregnant women about CMV and supporting behavior changes can reduce seroconversion rates, though the evidence base remains modest in size.25PubMed. Hygiene interventions for prevention of cytomegalovirus infection among childbearing women: systematic review A more recent review confirmed that these measures are acceptable to pregnant women and can meaningfully change behavior.26The Pediatric Infectious Disease Journal. Prevention of Acquisition of Cytomegalovirus Infection in Pregnancy Through Hygiene-based Behavioral Interventions: A Systematic Review and Gap Analysis The challenge is that you cannot practice precautions you have never heard of, which circles back to the awareness problem: if most pregnant women do not know CMV exists, they are not in a position to act on prevention advice.27PubMed Central. Prevention of maternal and congenital cytomegalovirus infection
Treatment for Congenital CMV
When a newborn is identified with symptomatic congenital CMV, antiviral treatment with valganciclovir is the current standard of care. The key trial in this space found that six months of oral valganciclovir, compared to just six weeks, produced better hearing outcomes: about 73% of babies in the longer-treatment group had improved or stable hearing at 12 months, compared to 57% in the shorter-treatment group. That benefit held at 24 months, and the six-month group also showed better language development scores.28PubMed Central. Valganciclovir for symptomatic congenital cytomegalovirus disease
Treatment is not without trade-offs. The main side effect is neutropenia, a drop in a type of white blood cell that fights infection, which occurred in roughly one in five babies in the trial. Infants on treatment need regular blood monitoring to watch for this and other complications like kidney or liver stress.29Clinical and Experimental Pediatrics. Treatment of congenital cytomegalovirus infection Timing matters: antiviral treatment is recommended within the first month of life, and infants with life-threatening symptoms may start with intravenous ganciclovir before switching to oral valganciclovir. Overall, neonatal antivirals have been described as moderately effective and generally well-tolerated, though treatment protocols still vary among hospitals.30PubMed Central. Role of Valganciclovir in Children with Congenital CMV Infection: A Review of the Literature
The Economic Weight of Congenital CMV
Congenital CMV does not get the public attention of Down syndrome or neural tube defects, yet its economic footprint is enormous. The US Institute of Medicine estimated the annual societal cost of congenital CMV at roughly $4 billion in 1995 dollars, which translates to about $6.6 billion when adjusted to 2018 levels.31PubMed Central. Economic assessments of the burden of congenital cytomegalovirus infection and the cost-effectiveness of prevention strategies That figure accounts for hearing aids, cochlear implants, special education services, long-term disability support, and medical care for children with neurological damage. It is a sobering number for a virus most people have never heard of.
Where Vaccine Development Stands
A CMV vaccine has been called one of the highest-priority targets in infectious disease prevention for decades, and the field is closer now than it has ever been. The leading candidate is mRNA-1647, developed by Moderna, which uses the same messenger RNA platform as some COVID-19 vaccines. Phase 1 and 2 trials showed that the vaccine produced strong neutralizing antibody responses in both people who had never been infected and those who already carried the virus, with immune responses lasting at least 18 months after vaccination.32PubMed Central. The mRNA-1647 vaccine: A promising step toward the prevention of cytomegalovirus infection (CMV) The Phase 2 results supported moving to a Phase 3 trial, called CMVictory, which is evaluating the vaccine in women of childbearing age with the goal of preventing congenital CMV transmission.33PubMed Central. Safety and Immunogenicity of mRNA-1647, an mRNA-Based Cytomegalovirus Vaccine in Healthy Adults: Results of a Phase 2, Randomized, Observer-Blind, Placebo-Controlled, Dose-Finding Trial
Multiple other vaccine candidates are also in development, including approaches targeting transplant recipients. A 2024 expert meeting concluded that, with the number and quality of candidates now in clinical trials, a safe and effective CMV vaccine appears within reach, though challenges remain around trial design and demonstrating efficacy against both congenital infection and transplant-related disease.34PubMed Central. A vaccine against cytomegalovirus: how close are we? If any of these vaccines prove successful, the impact could be substantial given that the virus affects thousands of newborns each year and costs the healthcare system billions.