The Zika virus is likely to spread across nearly all of the Americas, the World Health Organization has warned.
The infection, which causes symptoms including mild fever, conjunctivitis and headache, has already been found in 21 countries in the Caribbean, North and South America.
It has been linked to thousands of babies being born with underdeveloped brains and some countries have advised women not to get pregnant.
No treatment or vaccine is available.
The virus was first detected in 1947 in monkeys in Africa. There have since been small, short-lived outbreaks in people on the continent, parts of Asia and in the Pacific Islands.
But it has spread on a massive scale in the Americas, where transmission was first detected in Brazil in May 2015.