The Zika virus has been linked to a birth defect a family in Cape Cod is enduring.Weeks into Melissa Therrien’s pregnancy, doctors noticed that her daughter Alainah’s head was not growing. Her daughter was born prematurely with a microcephaly, a condition associated with incomplete brain development.At first glance, 15-month-old Alainah appears to be a happy, healthy toddler, but her parents are teaching her sign language in case her speech never fully develops.“She’s our own unique baby,” said Therrien. “She teaches us things that if she wasn’t with microcephaly, we would have never learned.”The cause of Therrien’s daughter’s condition is not known, but as the Zika virus rapidly spreads across Latin America, complicating thousands of pregnancies, Therrien and her husband hope to somehow help families that are facing struggles they know so well.“I want to give them the foundation of having support,” said Therrien. “That’s the one thing I haven’t found - emotionally.”