ZIKA VIRUS VERTICAL TRANSMISSION IN CHILDREN WITH CONFIRMED ANTENATAL EXPOSURE

ABSTRACT Background In utero transmission of Zika virus (ZIKV) can lead to adverse infant outcomes, but vertical transmission rates are unknown. Methods Antenatally ZIKV-exposed children were followed prospectively since the time of the Rio de Janeiro epidemic in 2015-16. Serum and urine specimens were collected from infants from birth throughout the first year of life. Specimens were tested by quantitative reverse transcriptase polymerase chain reaction (PCR) and/or IgM antibody capture Zika MAC-ELISA. Infants had neurodevelopmental evaluations, brain imaging, eye examinations, and hearing assessments. Results Over time 130 in utero ZIKV-exposed (mothers PCR+) children were tested with 407 specimens evaluated: 161 sera were tested by PCR and IgM assays, 85 urines by PCR; 84 children (65%) were positive in at least one assay. Among 94 children tested within 3 months of age, 70% were positive (39% serum PCR, 48% urine PCR, 39% IgM). After 3 months, 33% were positive by any laboratory method. Five children were intermittently PCR+ beyond 200 days of life. Concordance between IgM and PCR results was 52%, sensitivity 65%, specificity 40% (with any positive PCR result as the gold standard); IgM and serum PCR were 61% concordant; serum and urine PCR 55%. Most children (65%) were clinically normal. Positive results were seen in 29 of 45 children (64%) with abnormal findings and 55 of 85 normal children (65%), p=0·98. Earlier maternal trimester of infection was associated with positive infant laboratory results but not infant clinical disease (p=0·04). Conclusions ZIKV has a high in utero transmission rate. Laboratory confirmed infection is not necessarily associated with abnormal infant findings.