Rosana Vieira Alves (R rear) bathes her 4-month-old daughter Luana Vieira, who was born with microcephaly, as her daughters Vitoria Evillen (L) and Laiane Sophia play outside their home in Olinda, Brazil, February 3, 2016. The suspected link between the Zika virus and a birth defect known as microcephaly appears "stronger and stronger" as researchers study whether there is a causal connection, the head of the U.S. Centers for Disease Control and Prevention said on Friday. Picture taken February 3, 2016. REUTERS/Ueslei Marcelino