Zika’s million-dollar question: Where are the birth defects?
A curious conclusion is emerging: While the virus has spread like wildfire across the Americas, outside Brazil, an epidemic of birth defects has not.

Tens of thousands of Zika cases have been confirmed or suspected in countries like Colombia, Venezuela and Nicaragua since late 2015. The infected have included thousands of pregnant women. But those infections have not led to a dramatic rise in reported birth defects like microcephaly, in which a baby develops an abnormally small head and brain...