An Anonymous Coward writes:
The Zika virus has been known for quite some time, but it gained notoriety recently due to its possible linkage to birth defects.
Science News has a summary report on Zika virus: https://www.sciencenews.org/article/special-report-heres-what-we-know-about-zika
A report on the studies of its possible linkage to microcephaly, a birth defect of babies with undersized and underdeveloped brains: https://www.sciencenews.org/article/how-zika-became-prime-suspect-microcephaly-mystery
In short, studies are continuing, evidence is mounting, but still not quite a confirmation.
As a group, biologists don't seem to put much effort into figuring out the consequences of their theories or designing studies to rule out as many explanations as possible. That is probably why.