A four-year survey of more than 100,000 newborn babies in north-eastern Brazil has uncovered hitherto unrecognised patterns of microcephaly. The discovery suggests microcephaly is not necessarily a new phenomenon, and questions whether Zika virus is even the cause. Paediatric cardiologist Dr Sandra Mattos ... and her colleagues surveyed more than 100,000 newborns for congenital heart disease in the Brazilian state of Paraiba. We tried to establish the pattern of microcephaly over the last four years," Dr Mattos said. "What we expected was that we would have something like ... what has been documented in the official sites. "But we then noticed that we had much, much higher numbers. "Independent of what criteria we used, we had between 2-8 per cent of babies that would fall into the criteria of microcephaly," she said. This represents between 2,000 and 4,000 babies per year in the state of Paraba - about 1,000 times more than the team expected. The survey goes back to 2012 and 2013 and shows a spike each spring and summer, and while the headlines are all recent, the biggest peak in north-eastern Brazil was actually in 2014. The survey calls into question whether these microcephaly cases are caused by Zika virus or something else. If it is Zika virus, it has been in Brazil for a lot longer than people have thought, but that does not explain why after 50 years Zika has only now been linked to microcephaly.