Cytomegalovirus (CMV) Transmission: Routes, Risks, and Prevention

CMV Overview

CMV is a ubiquitous betaherpesvirus. Primary infection is usually asymptomatic in immunocompetent hosts but establishes lifelong latency with periodic reactivation. Seroprevalence: 40–100% globally, increasing with age.

Transmission Routes

Route	Details	Risk Context
Direct contact with body fluids	Saliva, urine, tears, semen, cervical/vaginal secretions, breast milk, blood	Kissing, sexual contact, diaper changing, breastfeeding
Vertical (mother-to-child)	Transplacental (primary > reactivation), intrapartum (genital tract), postnatal (breast milk)	Primary infection in pregnancy: 30–40% transmission; congenital CMV = leading infectious cause of birth defects
Transfusion/transplant	Leukoreduction and CMV-seronegative products reduce risk	Immunocompromised recipients at risk for CMV disease
Indirect (fomites)	Virus survives hours on surfaces	Toys, utensils, towels – minor role

High-Risk Groups for Severe Disease

• Fetuses (congenital CMV: hearing loss, neurodevelopmental delay, microcephaly)
• Transplant recipients (solid organ, HSCT) – CMV syndrome, tissue-invasive disease
• HIV/AIDS (CD4 <50) – retinitis, colitis, encephalitis
• Neonates (preterm, LBW) – sepsis-like syndrome

Prevention Strategies

• Pregnant women/caregivers of young children: Hand hygiene after diaper changes, avoid sharing food/utensils/kissing on lips, don't put pacifiers in own mouth.
• Transplant candidates: Serostatus matching (D+/R– highest risk); antiviral prophylaxis (valganciclovir) or preemptive therapy guided by PCR monitoring.
• Blood products: Leukoreduction; CMV-seronegative for at-risk recipients.
• Safe sex: Condoms reduce sexual transmission.

Vaccines

No licensed CMV vaccine yet. Several candidates in clinical trials (mRNA, vectored, subunit) targeting glycoprotein B and pentameric complex.