Prevalence and clinical profile of microcephaly in South America pre-Zika, 2005-14: prevalence and case-control study
Iêda M Orioli1,2, Helen Dolk3, Jorge S Lopez-Camelo2,4
1Latin American Collaborative Study of Congenital Malformations (ECLAMC) at Department of Genetics, Institute of Biology, Federal University of Rio de Janeiro, 21944-001, Rio de Janeiro, Brazil.
Abstract:
Objective To describe the prevalence and clinical spectrum of microcephaly in South America for the period 2005-14, before the start of the Zika epidemic in 2015, as a baseline for future surveillance as the Zika epidemic spreads and as other infectious causes may emerge in future.Design Prevalence and case-control study.Data sources ECLAMC (Latin American Collaborative Study of Congenital Malformations) database derived from 107 hospitals in 10 South American countries, 2005 to 2014. Data on microcephaly cases, four non-malformed controls per case, and all hospital births (all births for hospital based prevalence, resident within municipality for population based prevalence). For 2010-14, head circumference data were available and compared with Intergrowth charts.Results 552 microcephaly cases were registered, giving a hospital based prevalence of 4.4 (95% confidence interval 4.1 to 4.9) per 10 000 births and a population based prevalence of 3.0 (2.7 to 3.4) per 10 000. Prevalence varied significantly between countries and between regions and hospitals within countries. Thirty two per cent (n=175) of cases were prenatally diagnosed; 29% (n=159) were perinatal deaths. Twenty three per cent (n=128) were associated with a diagnosed genetic syndrome, 34% (n=189) polymalformed without a syndrome diagnosis, 12% (n=65) with associated neural malformations, and 26% (n=145) microcephaly only. In addition, 3.8% (n=21) had a STORCH (syphilis, toxoplasmosis, other including HIV, rubella, cytomegalovirus, and herpes simplex) infection diagnosis and 2.0% (n=11) had consanguineous parents. Head circumference measurements available for 184/235 cases in 2010-14 showed 45% (n=82) more than 3 SD below the mean, 24% (n=44) between 3 SD and 2 SD below the mean, and 32% (n=58) larger than -2 SD.Conclusion Extrapolated to the nearly 7 million annual births in South America, an estimated 2000-2500 microcephaly cases were diagnosed among births each year before the Zika epidemic began in 2015. Clinicians are using more than simple metrics to make microcephaly diagnoses. Endemic infections are important enduring causes of microcephaly.
Insights
Microcephaly prevalence in South America before the 2015 Zika epidemic was estimated at 3.0-4.4 per 10,000 births. Endemic infections and genetic factors were significant causes, highlighting the need for ongoing surveillance.
Area of Science:
- Pediatrics
- Epidemiology
- Genetics
Background:
- Microcephaly is a critical indicator of potential developmental abnormalities.
- Establishing baseline prevalence before the Zika epidemic is crucial for future public health surveillance.
- Understanding the clinical spectrum of microcephaly aids in identifying diverse etiologies.
Purpose of the Study:
- To determine the prevalence and clinical characteristics of microcephaly in South America from 2005-2014.
- To establish a baseline for microcephaly surveillance prior to the Zika virus epidemic.
- To identify common causes and clinical presentations of microcephaly in the region.
Main Methods:
- A prevalence and case-control study design was employed.
- Data were sourced from the ECLAMC database (Latin American Collaborative Study of Congenital Malformations) across 10 South American countries (2005-2014).
- Hospital-based and population-based prevalence were calculated, with head circumference data compared to Intergrowth charts for cases from 2010-2014.
Main Results:
- A total of 552 microcephaly cases were registered, with hospital-based prevalence at 4.4/10,000 births and population-based prevalence at 3.0/10,000 births.
- Significant variations in prevalence were observed across countries, regions, and hospitals.
- Common associations included diagnosed genetic syndromes (23%), polymalformations without syndrome diagnosis (34%), neural malformations (12%), and STORCH infections (3.8%).
Conclusions:
- An estimated 2000-2500 microcephaly cases occurred annually in South America before 2015.
- Diagnosis of microcephaly involves more than simple head circumference measurements.
- Endemic infections represent important, persistent causes of microcephaly, necessitating continued monitoring.
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