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    Zika screening: Is looking for microcephaly enough?


    A case series published in The Lancet appears to indicate that normal head circumference alone is insufficient to rule out congenital Zika virus in infants whose mothers could have been infected.

    The findings reflect a review by Brazilian researchers of 1501 liveborn infants whose cases had been investigated by medical teams at the State level through February 27, 2016. The suspected Zika cases were classified into 5 categories, based on neuroimaging and laboratory results: definite cases with laboratory evidence of Zika virus infection; highly probable cases with specific neuroimaging findings and no positive results for other congenital infections; moderately probably cases with specific neuroimaging findings but other infections could not be ruled out; somewhat probable cases, which had neuroimaging findings but for which there was not enough detail provided by the local teams; and all other cases. InterGrowth standards were used to assess head circumference by gestational age. State medical teams provided information on history of rash and first week mortality.

    Of the 1501 suspected cases, 899 were discarded. Of the remaining 602 cases, 76 were definite; 54 were highly probably; 181 were moderately probable; and 291 were somewhat probable of having congenital Zika virus. Among the 4 groups, the clinical, anthropometric, and survival differences were small. When compared to the 4 groups, the discarded cases had larger head circumferences (mean Z scores −1.54 vs −3.13, difference 1.58 [95% confidence interval {CI} 1.45–1.72]); lower first week mortality (14 per 1000 vs 51 per 1000; rate ratio 0.28 [95% CI 0.14–0.56]); and were less likely to have a history of rash during the pregnancy (20.7% vs 61.4%, ratio 0.34 [95% CI 0.27–0.42]). A history of rash during the third trimester was linked with brain abnormalities in spite of normal head circumference. One in 5 definite or probable cases presented with a head circumference in the normal range (above −2 SD below the median of the InterGrowth standard). Additionally one-third of definite and probable cases had no history of rash during the pregnancy.

    The researchers concluded that many definite and probable cases of congenital Zika virus can be found in infants with normal heard circumference whose mothers may not have reported having a rash during pregnancy. They urged that screening criteria be updated so that affected babies aren’t missed.

    NEXT: Are women more likely to survive cardiac arrest than men?

    Miranda Hester
    Ms. Hester is Content Specialist with Contemporary OB/GYN and Contemporary Pediatrics.


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