Risk Factors for Cytomegalovirus Reinfections in Seropositive Women

Increased cytomegalovirus (CMV) exposure and reinfections in seropositive pregnant women may be associated with exposure to young children and crowded living conditions, according to a study published in Clinical Infectious Diseases.

CMV shedding in bodily fluids has not been well-defined, especially in pregnancy. Regardless of universal CMV seroprevalence in childbearing-aged women, congenital CMV infection is reportedly higher in developing countries. To understand this trend, define transmission risk factors, and provide insight into sources and routes of virus acquisition in maternal populations, this prospective study characterized CMV shedding patterns and viral loads in saliva, urine, vaginal secretions, and blood at different stages of pregnancy within a highly CMV-seropositive population.

One hundred and twenty CMV-seropositive, pregnant women (<15 weeks’ gestation; mean age, 24 years) from Brazilian healthcare centers were enrolled at their first antenatal visit with follow-up evaluations in the second and third trimesters of gestation and 1 month after delivery. Overall, 2512 specimens were collected and tested. In addition, the association between exposure to young children, household crowding, and/or sexual activity and increased CMV shedding frequency was explored.

This study was the first to define CMV shedding characteristics in saliva during pregnancy. Findings suggest that contact with saliva is a route of viral spread from seropositive pregnant women. Overall, 35.0% of women shed CMV at least once in saliva (20.0%), urine (13.3%), genital secretions (12.5%), and/or blood (0.8%) during the study. CMV DNA was more frequently detected in saliva than in vaginal secretions during the first (10.0% vs 1.7%) and second (8.3% vs 1.6%) trimesters. In addition, only during the first trimester was CMV more commonly detected in saliva than urine (10.0% vs 2.5%). In contrast to previous studies, results were unable to show increasing shedding rates during gestation.

CMV DNA was detected in 61.3% of breast milk specimens and depended on the timing of milk collection after delivery: <30 days, 84.6%; 30-45 days, 64.8%; and >45 days, 42.4%. When compared with other specimens, breast milk showed a significantly higher mean viral load of 4.14 log10(SD=1.09) IU/mL (P <.01 for all multiple comparisons). The mean viral loads in bodily fluids (saliva, urine, vaginal secretions, breast milk samples) during gestation and postpartum were 2.70 log₁₀ (standard deviation, 0.73) IU/mL and 2.85 log₁₀ (standard deviation, 0.68) IU/mL.

CMV shedding was independently associated with household crowding (≥2 persons per room) and exposure to children. Mothers exposed to young children were twice as likely to shed virus as those who were not (58% vs 26%). Of those who did not shed, 74.3% reported no contact with children <2 years old and 65.4% reported no contact with children 3 to 6 years old. Women living in crowded households were more likely to shed virus (64% vs 31%) because of their close contact with others. Sexual activity was not associated with viral shedding.

Results provide an alternative explanation for virus acquisition and shedding in seroimmune pregnant women. The study authors concluded that results serve “as reference data for designing rational and cost-effective interventions that could significantly decrease the birth prevalence of congenital CMV infection in this population and likely in other maternal populations with high CMV seroprevalance.”

Reference

Barbosa NG1, Yamamoto AY1, Duarte G, et al. Cytomegalovirus (CMV) shedding in seropositive pregnant women from a high seroprevalence population: “the brazilian cytomegalovirus hearing and maternal secondary infection study” (BraCHS) [published online February 27, 2018]. Clin Infect Dis. doi: 10.1093/cid/ciy166