Role of breast milk in acquisition of cytomegalovirus infection: Recent advances

Purpose of review: Congenital infection with cytomegalovirus is a major cause of disability in newborns. Recently, there has been increased emphasis on the study of postnatally acquired cytomegalovirus infection. One route by which cytomegalovirus infections are acquired in newborns is via consumption of breast milk from cytomegalovirus-seropositive, lactating mothers. The purpose of this review is to summarize recent studies of breast-milk-acquired cytomegalovirus infections in newborns, particularly in low-birth-weight premature infants. Recent findings: Nearly all cytomegalovirus-seropositive women will reactivate and shed cytomegalovirus during lactation, as demonstrated by sensitive polymerase chain reaction techniques, as well as by viral culture of breast milk. A substantial proportion of infants exposed to cytomegalovirus in breast milk will acquire a primary cytomegalovirus infection. Although acquisition of cytomegalovirus by this route is seldom of consequence in healthy term infants, cytomegalovirus infections in low-birth-weight premature infants have been demonstrated to cause symptomatic illness, including hepatitis, neutropenia, thrombocytopenia, and a 'sepsis-like' state. Summary: Cytomegalovirus is commonly shed in human milk, and cytomegalovirus-seropositive women can transmit this infection via breast-feeding. The benefits of breast-feeding greatly outweigh the minimal risk, if any, of infections transmitted to term infants. Caution is warranted, however, in low-birth-weight premature infants, who are at increased risk of cytomegalovirus disease. Interventions to screen breast milk, or to attempt to render breast milk noninfectious through treatments such as freezing, may be warranted in high-risk premature infants.