Vanessa, 32, types a text message on her mobile phone as she holds her daughter Valentina, who is 5-months-old and born with microcephaly, inside of their house in Jaboatao, near Recife, Brazil, February 12, 2016. The Zika virus may be particularly adept at entrenching itself in parts of the body that are shielded from the immune system, making it harder to fight off and possibly lengthening the timeframe in which it can be transmitted, top U.S. experts said on Friday. Picture taken February 12, 2016. REUTERS/Nacho Doce