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Colombia began official surveillance for Zika virus disease (ZVD) in August 2015 and declared the country's first ZVD outbreak in October 2015. This report summarizes current epidemiology and birth outcomes of ZVD based on surveillance by the Colombian Instituto Nacional de Salud.
Between August 9, 2015, and April 2, 2016, 65,726 cases of ZVD were reported, 11,944 of which occurred in pregnant women. Of 3384 cases with laboratory testing for Zika (60% in pregnant women), 73% tested positive. ZVD incidence was higher in females than in males >4 years old, particularly in women aged 25 to 29 (345.0 per 100,000); the highest female-to-male incidence ratio was observed in the 20- to 24-year-olds (3.42). Most pregnant women with ZVD had not delivered by the study's end; among infants of 616 women diagnosed with ZVD during the third trimester, none had microcephaly or another brain abnormality reported, and 82% were full-term with normal birth weights. Of 50 cases of possible microcephaly in infants reported between January 1 and April 28, 2016, 4 were associated with Zika virus infection, although the mothers were not symptomatic during pregnancy.
Pacheco O et al. Zika virus disease in Colombia — preliminary report. N Engl J Med 2016 Jun 15; [e-pub]. (http://dx.doi.org/10.1056/NEJMoa1604037)
Comment
This report from Colombia highlights the rapid spread of the Zika outbreak. The higher incidence rates in females than in males in most age groups could be explained by reporting bias in women of childbearing age, but this bias does not explain the difference for younger girls and older women. Of concern, the only cases of microcephaly attributable to Zika occurred in infants born to women with asymptomatic ZVD. We await further information regarding outcomes in women infected earlier in pregnancy.