Background: The disease Zika is considered as emergent. The infection can be acquired through different routes: a bite from the Aedes mosquito, sexual contact, from mother to child during pregnancy and by blood transfusion. The possibility of Zika transmission through human lactation has been considered. Zika is a disease of great concern for public health because it has been associated with neonatal and postnatal microcephaly, among other birth defects.
Objectives: To review published evidence of the probable transmission of Zika through human lactation.
Data sources: Electronic databases: Cochrane Central Register of Controlled Trials, EBSCO, Gale, Science Direct, Scopus, US National Library of Medicine (PubMed) and Web of Science. World Health Organization and Centers for Disease Control and Prevention web pages.
Study eligibility criteria: To be eligible, studies of any design had to provide primary data of human breast milk as a potential fluid for the transmission of Zika, or primary or secondary follow-up data of infants with at least one previous published study that complied with the first criterion of eligibility.
Participants: Studies about women with suspected, probable or confirmed Zika during pregnancy, or the postnatal period and beyond. Studies about infants who breastfeed directly from the breast or where fed with the expressed breast milk of the suspected, probable or confirmed women with Zika.
Results: This study only chose data from research papers; no patients were taken directly by the authors. A total of 1,146 were screened and nine studies were included in the qualitative synthesis, from which a total of 10 cases were identified, with documented follow-up in three of these cases. Through the timing of maternal Zika infection, five cases were classified as prenatal (time before delivery), one as immediate postnatal (period from 0 to 4 days after birth); no cases were classified as medium postnatal (period from 5 days to 8 weeks after birth); two were classified as long postnatal (period from 8 weeks to 6 months after birth) and two as beyond six months after birth.
Conclusion: Human milk may be considered as a potentially infectious fluid, but we found no currently documented studies of the long-term complications in infants up to 32 months of age, with suspected, probable or confirmed Zika through human lactation, or evidence with respect to the human pathophysiology of the infection acquired through human lactation. In the light of the studies reviewed here, the World Health Organization recommendation of June 29th 2016, remains valid: "the benefits of breastfeeding for the infant and mother outweigh any potential risk of Zika virus transmission through breast milk."
Keywords: Human lactation; Human-milk; Nursing mother; Transmission; Zika.