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Increase in reported prevalence of microcephaly in infants born to women living in areas with confirmed Zika virus transmission during the first trimester of pregnancy — Brazil, 2015
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    Recommendations for pregnant women considering travel to an area of Zika virus transmission -- Recommendations for pregnant women with history of travel to an area of Zika virus transmission -- How to treat pregnant women with diagnoses of Zika virus disease.

    Widespread transmission of Zika virus by Aedes mosquitoes has been recognized in Brazil since late 2014, and in October 2015, an increase in the number of reported cases of microcephaly was reported to the Brazil Ministry of Health.* By January 2016, a total of 3,530 suspected microcephaly cases had been reported, many of which occurred in infants born to women who lived in or had visited areas where Zika virus transmission was occurring. Microcephaly surveillance was enhanced in late 2015 by implementing a more sensitive case definition. Based on the peak number of reported cases of microcephaly, and assuming an average estimated pregnancy duration of 38 weeks in Brazil (1), the first trimester of pregnancy coincided with reports of cases of febrile rash illness compatible with Zika virus disease in pregnant women in Bahia, Paraíba, and Pernambuco states, supporting an association between Zika virus infection during early pregnancy and the occurrence of microcephaly. Pregnant women in areas where Zika virus transmission is occurring should take steps to avoid mosquito bites. Additional studies are needed to further elucidate the relationship between Zika virus infection in pregnancy and microcephaly.

    What is already known about this topic? An outbreak of Zika virus disease, caused by a flavivirus transmitted by Aedes mosquitoes, occurred in Brazil in early 2015. An increase in the prevalence of infants born with microcephaly has been reported in Brazil since October 2015, in association with clusters of febrile rash illness in pregnant women.

    What is added by this report? The birth prevalence of microcephaly in Brazil increased sharply during 2015–2016. The largest increase occurred in the Northeast region, where Zika virus transmission was first reported in Brazil. This analysis of 574 cases of microcephaly, detected through a newly established ad hoc microcephaly surveillance system, identified temporal and geospatial evidence linking the occurrence of febrile rash illness consistent with Zika virus disease during the first trimester of pregnancy with the increased birth prevalence of microcephaly. The prevalence of microcephaly in 15 states with laboratory-confirmed Zika virus transmission (2.8 cases per 10,000 live births) significantly exceeded that in four states without confirmed Zika virus transmission (0.6 per 10,000).

    What are the implications for public health practice? The suggested link between maternal exposure to Zika virus infection during the first trimester of pregnancy and the increased birth prevalence of microcephaly provide additional evidence for congenital infection with Zika virus. Ongoing surveillance is needed to identify additional cases and to fully elucidate the clinical spectrum of illness. Pregnant women should protect themselves from mosquito bites by wearing protective clothing, applying insect repellents, and when indoors, ensuring that rooms are protected with screens or mosquito nets.

    Suggested citation for this article: Kleber de Oliveira W, Cortez-Escalante J, De Oliveira WT, et al. Increase in Reported Prevalence of Microcephaly in Infants Born to Women Living in Areas with Confirmed Zika Virus Transmission During the First Trimester of Pregnancy — Brazil, 2015. MMWR Morb Mortal Wkly Rep. ePub: 8 March 2016. DOI: http://dx.doi.org/10.15585/mmwr.mm6509e2er.


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