Prevalence of Zika, dengue and Chikungunya virus infection in pregnant women and surveillance of congenital Zika infection in Salvador, Brazil

Abstract

Background: An unprecedented outbreak of Zika virus (ZIKV) occurred in Brazil in 2015. Approximately 18,372 cases were notified in the city of Salvador, located in the state of Bahia in northeastern Brazil. Methods & Materials: Beginning in February 2016, active hospital surveillance for congenital Zika virus infection and a cross-sectional study at a reference maternity hospital were initiated to evaluate the prevalence of recent and previous infections by ZIKV, Dengue and Chikungunya virus in pregnant women as well as congenital infection by ZIKV in newborns. Results: To date, we have enrolled 224 women and 223 newborns. The mean age of women is 25 ± 6 years, with 146 (61%) reporting an exanthematous illness during pregnancy. The majority of these cases occurred between February and April 2016. Most babies were born by vaginal delivery (60%) at gestational age of 37.4 ± 5 weeks. Most (53%) of the newborns were male and 48 (21.5%) were diagnosed with microcephaly. Of these, 16 (33%) were admitted to a neonatal intensive care unit and four (8.3%) died. Many women (n = 133) were tested by ELISA IgG for Zika, Dengue and Chikungunya at the time of delivery. The majority (94%) were Dengue IgG positive, 94 (71%) were Zika IgG positive and 39 (28.6%) presented Chikungunya IgG positivity. Positive ELISA IgM for Zika in mothers and newborns was 7.4% and 5.6% respectively. ZIKV RT-PCR was performed in 114 samples from newborns (umbilical cord blood and urine), yielding 17 (15%) positive results, five of which were from microcephalic babies, while 12 were normocephalic. ZIKV RT-PCR positivity was 19.2% in microcephalic newborns and 13.6% in normocephalic newborns. Conclusion: In light of these findings, we suggest that microcephaly should be considered a severe form of congenital Zika infection, and that less severe presentations should also be evaluated. We intend to further characterize the clinical manifestations associated with congenital ZIKV infection in a prospective follow-up study involving the babies with congenital ZIKV infection (with and without microcephaly) to more comprehensively describe the clinical manifestations, complications and natural history associated with ZIKV.