The World Health Organisation's Director-General Margaret Chan says 59 countries have reported cases of the Zika virus.

"You don't want to bring a standstill to the world's movement of people. For many reasons people go to travel, because tourism, because go to travel, because of studies, people go to travel to these countries because of business. So what is the proper way to deal with the risk? It's all about getting the best available evidence. Share with them so that individuals or groups of people can make appropriate measures to mitigate, to reduce the risks. It's all about risk assessment and risk management," she said.

Margaret Chan warned that health authorities needed to "work very hard" on the issue. She said the world had been "unprepared" for previous public health emergencies. Chan  said she shared the concerns of athletes and visitors over travelling to Rio de Janeiro for this summer's Olympic Games.