The World Health Organization has set up a Zika "emergency team" after the "explosive" spread of the virus.
Zika has been linked to thousands of babies being born with small brains in Brazil. WHO director general Dr Margaret Chan said Zika had gone "from a mild threat to one of alarming proportions" and was having a "heart-breaking" impact.
The team will meet on Monday to decide whether Zika should be treated as a global emergency.The last time an international emergency was declared was for the Ebola outbreak in West Africa which has killed more than 11,000 people.
Zika: What you need to know
Zika was first detected in Uganda in 1947, but has never caused an outbreak on this scale.
Brazil reported the first cases of Zika in South America in May 2015.
