Zika Virus-Associated Birth Defects, Costa Rica, 2016-2018

Abstract

After Zika virus (ZIKV) infection in Costa Rica was confirmed in January 2016, the national surveillance system was enhanced to monitor associated birth defects. To characterize the ZIKV outbreak among live-born infants during March 2016–March 2018, we conducted a descriptive analysis. Prevalence of ZIKV-associated birth defects was 15.3 cases/100,000 live births. Among 22 infants with ZIKV-associated birth defects, 11 were designated as confirmed (positive for ZIKV) and 11 were designated as probable cases (negative for ZIKV or not tested, but mother was expsed to ZIKV during pregnancy). A total of 91% had microcephaly (head circumference >2 SDs below mean for age and sex), 64% severe microcephaly (head circumference >3 SDs below mean for age and sex), 95% neurodevelopmental abnormalities, 82% brain anomalies, 41% eye abnormalities, and 9% hearing loss. Monitoring children for >1 year can increase identification of ZIKV-associated abnormalities in addition to microcephaly.

Keywords: Birth defects; Costa Rica; Zika virus; congenital infections; microcephaly; prevalence; surveillance; viruses.

Figure 1

Key events involving ZBD surveillance, Costa Rica, March 2016–March 2018. In Costa Rica, laboratory testing using real-time reverse transcription PCR was implemented in late January 2016 (–17). Although the first autochthonous case in Costa Rica was detected in a pregnant woman in February 2016 (16), a case was published in the United States about a traveler infected in December 2015 in Costa Rica (17). ZBD, Zika virus–associated birth defects.

Figure 2

Reported cases and classification of suspected cases of ZBD according to protocol, Costa Rica, March 2016–March 2018. rRT-PCR, real-time reverse transcription PCR; STORCH, syphilis, toxoplasmosis, rubella, cytomegalovirus, and hepatitis B (note that Costa Rica does not include hepatitis B in its standard evaluations); ZBD, Zika virus–associated birth defects.

Figure 3

Distribution of infants with reported ZBD and pregnant women with Zika virus infection, by month, Costa Rica, March 2016–March 2018. The peak of Zika virus infection among pregnant women occurred in September 2016; the highest number of suspected cases of ZBD occurred 6 months later, March–October 2017. ZBD, Zika virus–associated birth defects.

Figure 4

Prevalence of Zika-virus–associated birth defects (no. cases/100,000 live births), by province, Costa Rica, March 2016–March 2018. Cases are distributed by place of residence of the mother, not by place of birth. The 2 provinces in which prevalence of Zika virus–associated birth defects was highest (Puntarenas and Limón) are on the coast and have a humid tropical climate.