Study assesses the impact on babies of maternal infection by the zika virus

A national collaboration between researchers from Fiocruz and from 25 other Brazilian institutions grouped in the Brazilian Consortium of Cohorts related to the zika virus (ZBC Consortium), with support of the London School of Hygiene & Tropical Medicine (LSHTM), assessed the impact of infection by the zika virus during pregnancy on the health of the babies. Published in The Lancet Regional Health - Americas last Monday (November 28), the study showed that approximately one-third of the children born of mothers infected during pregnancy presented, in their first years of life, abnormalities consistent with congenital zika syndrome (CZS).

This was the research on the subject with the highest number of participants, managing to detect more clearly the relation between the zika virus and possible congenital conditions. The need for this evaluation arose after an epidemic of microcephaly in Brazil, in 2015, but the small samples, the high variability between the estimates, and the limitation of surveillance data limited the possibility to calculate the risks. The syndrome’s manifestations include functional neurological deficiencies, neuroimaging abnormalities, auditive and visual alterations, and microcephaly. These dysfunctions appear more frequently in an isolated fashion than in combination with others: less than 0.1% of the children exposed have two simultaneous dysfunctions.

The results were found after the combined analysis of data from 13 studies that investigate pediatric results in pregnancies affected by the zika virus during the 2015-2017 epidemic in Brazil. These data include all four regions of the country affected by the epidemic in that period, with prenatal infection confirmed at a laboratory level through genetic tests and evaluation of potential adverse effects on an individual level.

“This work provides a fundamental contribution to the understanding of the consequences for the health of infection by the zika virus during pregnancy. It brings together individual data of children born from 1,548 pregnant women residing in different regions of the country, who had a confirmed diagnosis of infection by the zika virus during pregnancy, which allowed for a more accurate estimate of the risks. It should also be highlighted that, in addition to the contribution in terms of knowledge, this study is a result of the competence of Brazilian researchers and public institutions in responding to scientific challenges: researchers first organized in their original institutions and then, jointly, created the Brazilian Consortium of Cohorts related to the zika virus”, stressed researcher Ricardo Arraes de Alencar Ximenes, of the University of Pernambuco and of the Federal University of Pernambuco (UFPE), who led the study.

As for microcephaly, a neurological condition in which the baby’s head is smaller than what is expected for its age and gender, one out of 25 children born of mothers infected by the zika virus during pregnancy presented this dysfunction at birth or during follow-up. In most cases, the condition was detectable near the moment of birth, but some babies born with normal head circumference developed microcephaly over the following years. The risk of children of mothers infected by the zika virus during pregnancy developing microcephaly was 2.6% at birth or when first evaluated, increasing to 4% in the first preschool years. This risk was considerably consistent in the different areas studied, with no variation observed regarding socioeconomic conditions or geographical area. 

At Fiocruz, five institutions contributed to the research: the National Institute of Women, Children and Adolescents Health Fernandes Figueira (IFF) and the Evandro Chagas National Infectiology Institute (INI), in Rio de Janeiro (RJ); the Leônidas and Maria Deane Institute (ILMD/Fiocruz Amazônia), in Manaus (AM); the Aggeu Magalhães Institute (IAM/Fiocruz Pernambuco), in Recife (PE); and the Gonçalo Moniz Institute (IGM/Fiocruz Bahia), in Salvador (BA).

Researcher Flor Ernestina Martinez-Espinosa, of Fiocruz Amazônia, is a senior co-author of the study (together with Patrícia Brasil, of INI/Fiocruz), and coordinated one of the cohorts of pregnant women exposed to the zika virus. The Manaus project took place following a partnership between Fiocruz and the Dr. Heitor Vieira Dourado Tropical Medicine Foundation (FMT-HVD), a reference institution for infectious and parasitic diseases in the state of Amazonas and home of two laboratories of Fiocruz Amazônia.

“We formed an inter and multidisciplinary group that followed more than 800 women who came to FMT-HVD with exanthematous diseases and who declared being pregnant; they were therefore reported as suspected cases of zika during pregnancy. This population was tested to confirm both events, pregnancy and infection by the zika virus. Three hundred and twenty cases were confirmed and 760 of the notified cases were followed up to the end of the pregnancy. We are currently engaged in an active search of the exposed children to analyze their situation in their first year of life”, said Martinez-Espinosa.
Additional studies with longer follow-ups are mentioned by the team of researchers as the future of the paper published this Monday.

Possible investigation options include the evaluation of the risk of hospitalization and death for children with microcephaly as they grow older and, in those without microcephaly, assessing the risks of other complications, such as those related to behavioral or neuropsychomotor development. The study also shows the importance of early diagnosis and intervention of any congenital manifestation attributed to the zika virus.