February 7, 2018

A key aim of ZikaPLAN’s Microcephaly Epidemic Research Group (MERG/ZikaPLAN; Work Package 1) is to unravel the factors - both biological and social - underpinning the development of severe congenital brain malformations in babies exposed to Zika virus in utero.

During the height of the Zika epidemic in Brazil, cases of microcephaly tended to occur in clusters concentrated in the Northeast. As the Northeast is one of the country’s poorest geographic regions and, like much of Brazil, continues to be challenged by a high degree of social inequality, scientists have hypothesized that local variations in socioeconomic conditions may have influenced the spatial distribution of the region’s microcephaly cases.

Working in partnership with the Pan American Health Organization, the Brazilian Ministry of Health, and the State Health Department of Pernambuco, members of the MERG/ZikaPLAN team examined the relationship between living conditions and microcephaly in the urban setting of Recife.  Recife, home to around 1.5 million residents, was a hotspot of the microcephaly epidemic, and during a one year period beginning in August 2015, the local health authorities registered nearly 350 microcephaly cases among the city’s newborns.  The full findings of this study by Souza and colleagues were reported in the January issue of BMC Public1.

Using an ecological approach, the investigators classified the 94 districts of Recife into four categories based on the percentage of household heads in each district whose monthly income was less than twice the minimum wage.  Onto this map of living conditions, they then overlaid the residential location for each microcephaly case.  The striking results show that, while a high number of cases could be mapped across the districts falling into the ‘low’ and ‘medium-low’ categories, microcephaly cases were remarkably rare in districts classified as having ‘high’ living conditions.  Moreover, looking at the temporal trends, the investigators also observed that microcephaly cases in the two wealthiest strata occurred only during the first 6 months of the epidemic.  Taken together, these findings provide evidence that individuals living in districts with more financial resources had a greater capacity to respond to the epidemic (e.g., by delaying pregnancy, pursuing terminations, and/or avoiding mosquito bites) than those from relatively deprived communities. The report concludes that these results indicate a strong association between poor living conditions and the prevalence of microcephaly.

This is not the first time that the association between precarious living conditions and Zika-related microcephaly has been discussed. Indeed, an earlier study has shown that nearly 90% of the babies registered with microcephaly between November 2015 and February 2016 were born in the Northeast region.  And on the individual level, several studies have provided evidence that women who had babies with microcephaly were more likely to be young, single, black, poor, and residents of smaller cities or living on the outskirts of larger ones.  Although it is difficult, at this point, to establish conclusive explanations for this pattern, there are some plausible hypotheses.  For example, it is thought that women with higher incomes may have differential access to health services and also have reduced exposure to the mosquitoes that carry Zika.

Overall, the findings from the MERG/ZikaPLAN investigators and their partners reinforce the idea that poverty may be both one social determinant and potential consequence of Zika infections during pregnancy.  Looking to the future, the on-going work of the MERG team and of others in the ZikaPLAN, ZIKAlliance, and ZIKAction consortia, will be pivotal for appraising the full cost of the microcephaly epidemic and for identifying the forms of public health support the affected children and their communities will require.

1 Microcephaly epidemic related to the Zika virus and living conditions in Recife, Northeast Brazil
BMC Public Health, 2018, Volume 18, Number 1, Page 1
Wayner Vieira de Souza, Maria de Fátima Pessoa Militão de Albuquerque, Enrique Vazquez, Luciana Caroline Albuquerque Bezerra, Antonio da Cruz Gouveia Mendes, Tereza Maciel Lyra, Thalia Velho Barreto de Araujo, André Luiz Sá de Oliveira, Maria Cynthia Braga, Ricardo Arraes de Alencar Ximenes, Demócrito de Barros Miranda-Filho, Amanda Priscila de Santana Cabral Silva, Laura Rodrigues, Celina Maria Turchi Martelli