Zika rash and increased risk of congenital brain abnormalities

According to different scenarios varying the expected prevalence rate--which is currently unknown in Brazil--the projected 87% sensitivity and 80% specificity observed for the combination of third-trimester rash and microcephaly would yield a minimal prevalence rate of 67·5% to obtain a positive predictive value of at least 90% (appendix), which represents an improbable scenario for a huge continental country like Brazil, where space would tend to mitigate the dynamic of the epidemic.