Geography of Microcephaly in the Zika Era: A Study of Newborn Distribution and Socio-environmental Indicators in Recife, Brazil, 2015-2016

Abstract

Objectives: We assessed sociodemographic and health care factors of mothers and newborns during a 2015-2016 outbreak of microcephaly in Recife, Brazil, and we analyzed the spatial distribution and incidence risk of newborns with microcephaly in relation to socio-environmental indicators.

Methods: We collected data from August 2015 through May 2016 from Brazil's Live Birth Information System and Bulletin of Microcephaly Notification, and we geocoded the data by maternal residence. We constructed thematic maps of districts, according to socio-environmental and vector indicators. We identified spatial aggregates of newborns with microcephaly by using the Bernoulli model. We performed logistic regression analyses to compare the incidence risk of microcephaly within socio-environmental indicator groups.

Results: We geocoded 17 990 of 19 554 (92.0%) live births in Recife, of which 202 (1.1%) newborns were classified as having microcephaly, based on a head circumference of ≥2 standard deviations below the mean. Larger proportions of newborns with microcephaly (compared with newborns without microcephaly) were born to mothers who delivered in a public hospital, did not attend college, were aged ≤19, or were black or mixed race. A higher risk of microcephaly (incidence rate ratio [IRR] = 3.90; 95% confidence interval [CI], 1.88-8.06) occurred in districts with the lowest (vs highest) Municipal Human Development Index (ie, an index that assesses longevity, education, and income). The risk of microcephaly was significantly higher where rates of larvae density (IRR = 2.31; 95% CI, 1.19-4.50) and larvae detection (IRR = 2.04; 95% CI, 1.05-4.00) were higher and rates of sewage system (IRR = 2.20; 95% CI, 1.16-4.18) and garbage collection (IRR = 1.96; 95% CI, 0.99-3.88) were lower. Newborns with microcephaly lived predominantly in the poorest areas and in a high-risk cluster (relative risk = 1.89, P = .01) in the north.

Conclusions: The disproportionate incidence of microcephaly in newborns in poor areas of Recife reinforces the need for government and public health authorities to formulate policies that promote social equity and support for families and their children with microcephaly.

Keywords: Zika; ecological studies; environmental indicators; health inequalities; microcephaly; social indicators.

Figure 1.

Spatial distributions of newborns with microcephaly during an outbreak in the districts of Recife, Pernambuco, Brazil, August 2015–May 2016, by (a) Municipal Human Development Index (MHDI) 2010 and (b) community of social interest (CSI). The MHDI assesses levels of longevity, education, and income, and it ranges from 0 (low) to 1 (high). Data sources: Municipal Health Department Mortality Information System 2009-2011 (for longevity) and Brazilian Institute of Geography and Statistics Demographic Census 2010 (for education and income). CSIs are areas with precarious infrastructure (ie, homes are self-built and occupied by low-income families). Data source: Sanitation Authority of Recife for 2014.

Figure 2.

Spatial distributions of newborns with microcephaly during an outbreak in districts of Recife, Pernambuco, Brazil, August 2015–May 2016, by (a) Breteau index, (b) garbage-collection rate, and (c) sewage-system rate. The Breteau index is the number of water tanks testing positive for Aedes aegypti divided by the number of households investigated. A higher Breteau index indicates more households with water tanks testing positive for Aedes aegypti. Data source: Aedes aegypti Infestation Rapid Survey, October 2014 through December 2014 (unpublished data, Levantamento Rápido do Índice de Infestação por Aedes aegypti, 2016). The garbage-collection rate is defined as the proportion of households that receive garbage-collection services. The sewage- system rate is defined as the proportion of households with sewage systems. Data source: Brazilian Institute of Geography and Statistics Demographic Census 2010.

Figure 3.

Spatial clustering of low-risk and high-risk districts for newborns with microcephaly, Recife, Pernambuco, Brazil, August 2015–May 2016. The relative risk of microcephaly was defined as the calculated risk of microcephaly within a cluster divided by the calculated risk of it outside the cluster, which was derived from the relationship between numbers of observed and expected newborns with microcephaly. Data obtained from the Brazil Live Birth Information System and the Health Strategic Surveillance Information Center Platform of Recife.