Five new cases of Zika have been found in the tourist hotspot of Miami Beach, signalling that local transmission of a virus blamed for birth defects is spreading, Florida officials said Friday.

"This means we have a new area" of local transmission, said Governor Rick Scott.

Officials had previously said Zika was spreading in a one-square-mile (2.6-square-kilometer) zone north of downtown Miami called Wynwood, where more than two dozen people were believed to be infected by mosquitoes carrying the virus.