'I looked at him and a normal child and could see his head was smaller'
7 March 2016 Last updated at 23:23 GMT
A scientist leading a study in Brazil has told the BBC's Panorama programme there could be a whole new spike in cases in eight to nine months.
In Brazil the virus is suspected of leading to thousands of babies being born with underdeveloped brains.
The BBC's Jane Corbin has been to Recife to meet some families dealing with the condition.