Researchers said they found evidence in Venezuela that mother-to-child transmission of Zika virus through breast-feeding is possible.
Writing in Clinical Infectious Diseases, the researchers said the results of genetic testing of Zika virus isolates from a mother’s breast milk and her child’s urine “strongly suggest” transmission through breast-feeding.
Over the past 2 years, research spurred by an epidemic centered in Brazil has revealed that Zika virus infection during pregnancy can cause a pattern of serious fetal and infant birth defects, including microcephaly. According to a recent report, children affected by Zika virus may face challenges even beyond infancy, including seizure disorders and hearing or visual impairment. As of Dec. 21, nearly 600,000 cases of suspected Zika virus infection have been reported in the Americas since 2015, according to WHO.
The virus has been identified in breast milk before, including a study published last year in Emerging Infectious Diseases in which researchers reported detecting it 33 days after the onset of symptoms and 9 days after the woman delivered. But there is less evidence that it can actually be transmitted this way.
Currently, the CDC does not recommend against infected mothers breast-feeding, saying on its website: “Current evidence suggests that the benefits of breast-feeding outweigh the theoretical risk of Zika virus infection transmission through breast milk.” The agency told Infectious Disease News that it would consider the newly reported Venezuela case in its evaluation of new evidence about Zika but has not changed its clinical guidance for evaluating and managing pregnant women with Zika virus infection.
“At this time, CDC recommendations remain unchanged. Mothers are encouraged to breast-feed, even in areas where Zika virus is found,” Peggy Honein, PhD, MPH, acting director of the Division of Congenital and Developmental Disorders in the CDC’s National Center on Birth Defects and Developmental Disabilities, said.
The Venezuelan patient, aged 32, was exclusively breast-feeding her child, aged 5 months, when she presented with symptoms of Zika virus infection in March 2016. The child was asymptomatic. They both tested positive for the virus, which is primarily spread through the bite of infected female Aedes aegypti mosquitoes but also can be sexually transmitted by men and women and spread through blood transfusions or accidental laboratory exposure.
Whole genome sequencing of their isolates revealed almost identical strains that were different from other specimens in the laboratory, the researchers reported. The strains clustered with a Zika clade from Colombia. The woman had no history of traveling to Colombia but lived in Barquisimeto, a city the researchers identified as being on a major trade route to Columbia for Venezuelans facing food and medicine shortages back home.
“The mother and child lived in an air-conditioned, screened house, where the risk of mosquito transmission would be minimized,” the researchers noted. “They had no recent travel history, and the child spent most of the time within the house. While the source of the child’s infection cannot be determined, the virological and phylogenetic results of this study strongly suggest the occurrence of postnatal transmission from mother to child during breast-feeding.” – by Gerard Gallagher
Blohm GM, et al. Clin Infect Dis. 2017;doi:10.1093/cid/cix968.
CDC. Zika in infants and children. https://www.cdc.gov/pregnancy/zika/testing-follow-up/zika-in-infants-children.html. Accessed January 4, 2018.
Sotelo JR, et al. Emerg Infect Dis. 2017;doi:10.3201/eid2305.161538.
The authors report no relevant financial disclosures. Honein works for the CDC.