Three pregnant women in Florida have tested positive for Zika virus, the state's Department of Health announced Wednesday. All three women, whose names and locations were not released, traveled outside of the United States. The virus — primarily transmitted by the Aedes aegypti mosquito biting an infected person and spreading it — has been linked to Guillain-Barre, a rare syndrome that causes the immune system to attack nerves, and microcephaly, a neurological disorder that causes abnormally small heads and development issues in babies.