Zika–Microcephaly Link Confirmed in New Study

A study comparing babies born with microcephaly and closely matched, but otherwise healthy, controls has confirmed a link between the birth defect and Zika virus.

The study, published September 15 in the journal The Lancet Infectious Diseases, is not the first to find an association between the mosquito-borne virus and microcephaly. However, it is the first to confirm it, using healthy controls.

“When we compared laboratory-confirmed Zika virus infection in newborns with and without microcephaly, we found that about half of the cases with microcephaly had laboratory-confirmed Zika virus infection, compared to none of the healthy controls,” study co-author Thalia Velho Barreto de Araujo, PhD, of Federal University of Pernambuco in Recife, said in a statement released by The Lancet in conjunction with the article’s publication.

The research, which is being performed by a team from Brazil and the United Kingdom, is ongoing. However, The Lancet article reports on preliminary findings from 91 babies enrolled, including 30 born with microcephaly, between mid-January and the beginning of May at eight public hospitals in Pernambuco State, Brazil. The team compared rates of Zika infection between each of the babies born with microcephaly against two babies born without the defect the next morning at the same hospitals. Based on tests of the babies’ blood and cerebrospinal fluid, as well as blood tests from their mothers, the researchers found that 80% of the mothers who gave birth to a baby with microcephaly tested positive for Zika in their blood. Only 64% of the “control group” mothers tested positive.

The researchers plan to expand their investigation to 200 cases and 400 matched controls. Importantly, the investigators also emphasized that the reliability of blood and cerebrospinal fluid tests to screen for Zika virus in newborns is still unknown—in fact, 19 (59%) of the microcephalic babies enrolled in the study did not test positive for Zika.

Despite the limited evidence to date, the Centers for Disease Control and Prevention declared in April that maternal infection with Zika is a cause of infant microcephaly. The announcement was based on a New England Journal of Medicine study published earlier that month that found links between the virus and microcephaly, based on fetal and infant autopsy reports.

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.