Gleyse Kelly da Silva, bottom right, holds her daughter Maria Giovanna, who was born with microcephaly, outside their house in Recife, Pernambuco state, Brazil, Wednesday, Jan. 27, 2016. Brazilian officials still say they believe there's a sharp increase in cases of microcephaly and strongly suspect the Zika virus, which first appeared in the country last year, is to blame. The concern is strong enough that the U.S. Centers for Disease Control and Prevention this month warned pregnant women to reconsider visits to areas where Zika is present. (AP Photo/Felipe Dana)

UN health chief: Zika virus is ‘spreading explosively’

The Zika virus was first detected in 1947 and for decades only caused mild disease. The virus is now in more than 20 countries.