Brazilian researchers said that the discovery of Zika in the brains of babies with microcephaly adds to growing evidence of a link between the mosquito-transmitted virus and the birth defect.

"We have detected its presence in the brain tissue," Lucia Noronha, a pathologist from the Brazilian Society of Pathology, told AFP.

"The Zika virus caused brain damage and that reinforces evidence of a relationship between Zika and microcephaly," she said.