NEW YORK, N.Y. (WPVI) --Researchers are also learning more about HOW the Zika virus can cause the serious birth defect microcephaly.
Several mouse studies show when a mother is infected in the first trimester, when the placenta barrier is still immature.
The virus can pass through and limit blood flow to the baby.
It can also make its way to the brain and disrupt development.
Humans are very different from mice but the researchers say this gives them more information to help develop a vaccine.