What is the mode of spread of Cytomegalovirus (CMV)?

Modes of Transmission of Cytomegalovirus (CMV)

Cytomegalovirus (CMV) is transmitted through direct contact with infected bodily fluids including saliva, urine, genital secretions, breast milk, blood, and transplanted organs. 1, 2, 3

Primary Transmission Routes

Vertical Transmission

• Mother to child transmission occurs through several routes:
  • Congenital (in utero): Occurs in 0.2-2.2% of live births in the US 1
    • 30-40% transmission rate with primary maternal infection during pregnancy 1, 2
    • Lower transmission rate (0.15-1.0%) with recurrent maternal infection 1, 2
    • Occurs through placental transmission
  • Intrapartum: Through contact with infected cervical secretions during birth 1
  • Postpartum: Through breast milk containing infectious virus (up to 53% of breastfed infants may become infected) 1

Horizontal Transmission

• Direct contact with infected bodily fluids 1, 2, 3:
  • Saliva: Common route in early childhood, especially in settings with suboptimal sanitation 1
  • Urine: Important source of transmission, particularly in childcare settings 1, 4
  • Sexual contact: Major mode of acquisition among adolescents 1
    • Transmission through contact with virus-containing genital secretions 1, 4

Iatrogenic Transmission

• Blood transfusion: Through transfusion of cellular blood components (whole blood, red blood cells, platelets) 1, 2
• Organ transplantation: From infected donors to recipients 1, 2
• Stem cell transplantation: High risk in CMV-positive donors to CMV-negative recipients 1

Risk Factors for Transmission

• Age: Infection occurs at younger ages in locations with less optimal sanitation 1
• Socioeconomic status: Higher prevalence in lower socioeconomic strata (50-80% of women of childbearing age in the US) 1
• HIV coinfection: HIV-infected women have higher rates of CMV cervical shedding (52-59%) compared to HIV-uninfected women (14-35%) 1
• Immunosuppression: Higher risk of CMV disease in immunocompromised individuals 2

Prevention of Transmission

• Hygiene measures: Proper handwashing after contact with bodily fluids, especially after diaper changes 2, 3
• Avoiding sharing of utensils, food, and towels to prevent contact with potentially contaminated bodily fluids 1
• Safe sex practices: Using condoms to reduce sexual transmission 1
• Blood product screening: Use of CMV-negative or leukocyte-reduced blood products for high-risk recipients 1

Important Clinical Considerations

• CMV is the most common perinatally transmitted infection in the United States 1
• While transmission is common, symptomatic disease is less frequent when acquired through breast milk or intrapartum routes compared to congenital infection 1
• HIV-infected children appear to be at higher risk for acquisition of CMV during early childhood 1
• CMV can establish latency after primary infection with potential for reactivation during periods of immunosuppression 3, 5

Understanding these transmission routes is essential for implementing appropriate preventive measures, especially for pregnant women and immunocompromised individuals who are at highest risk for severe CMV disease.