CMV Exposure and Symptoms
The vast majority of people exposed to CMV remain asymptomatic—approximately 85-90% of congenital infections and most acquired infections in immunocompetent adults are clinically inapparent. 1
Asymptomatic Infection is the Norm
- Most CMV infections are asymptomatic or produce only mild, self-limited illness in immunocompetent individuals. 2
- In congenital CMV (cCMV), 85-90% of infected newborns are born with clinically inapparent infections and appear completely normal at birth. 1
- Among adults, the majority of primary CMV infections are asymptomatic, though CMV establishes lifelong latency with 40-100% seropositivity rates globally. 2
When Symptoms Do Occur
In Immunocompetent Adults
- Primary CMV infection causes up to 7% of mononucleosis syndrome cases (heterophil-negative mononucleosis), with symptoms nearly indistinguishable from Epstein-Barr virus mononucleosis. 3
- When symptomatic, patients may experience fever, sweats, weight loss, lymphocytosis, and hepatitis—these systemic symptoms can serve as useful diagnostic clues. 2
- Complications in immunocompetent adults are rare, though CMV can affect multiple organ systems including gastrointestinal tract, nervous system, eyes, and other organs. 2
In Congenital Infections
- Only 10-15% of infants with cCMV have clinically apparent disease at birth, presenting with jaundice, rash, enlarged liver/spleen, microcephaly, or small size for gestational age. 1, 4
- Over half of symptomatic newborns will develop long-term disabilities including hearing loss, intellectual disability, vision loss, and cerebral palsy. 1
Critical Caveat: Late-Onset Sequelae in "Asymptomatic" Cases
Even asymptomatic infections carry significant risk for delayed complications:
- Up to 20% of infants with asymptomatic cCMV will develop sensorineural hearing loss in childhood, with some studies showing rates as high as 25% by age 18. 1
- Hearing loss can be progressive and late-onset, appearing years after birth even when the infant appeared completely normal initially. 1
- Emerging research indicates nearly half of asymptomatic cCMV infants develop gaze, balance, and vestibular disorders. 1
High-Risk Populations
Certain groups are more susceptible to symptomatic disease despite immunocompetence:
- Critically ill patients in intensive care units 2
- Pregnant women (risk of fetal transmission and harm) 4
- Elderly patients 2
- Patients with inflammatory bowel disease 2
- Immunocompromised hosts (transplant recipients, HIV patients, CAR-T recipients) experience severe, tissue-invasive disease 5, 3, 6, 7
Clinical Implications
The asymptomatic nature of most CMV infections is precisely why screening programs are needed—clinical examination alone cannot identify the majority of infected individuals who remain at risk for serious long-term complications, particularly hearing loss in congenital cases. 1