Some women who get Zika have babies with severe birth defects, but some don’t.  In Brazil, some regions plagued with Zika have a huge percentage of babies with microencephaly.  But adjoining regions also plagued with Zika don’t.  Also, young, black, and poor women are being hit especially hard.

So researchers are now investigating whether Zika does its damage by being paired with other factors.  There had been speculation that the birth defects were caused by a government-administered pesticide.  But researchers have confirmed a direct link between the virus and the birth defects.  Still, things may not be so simple.

Now that Zika has come to the United States, 15 babies have been diagnosed with microencephaly related to the Zika virus.