The Zika virus, which has recently struck South and Central America at near-epidemic rates, could spread to the rest of the continent as well, according to the World Health Organization. The Zika virus causes devastating birth defects and is transmitted by mosquitoes, not thorough person-to-person contact.
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 is native to Africa and was first found to be spreading in the Americas in Brazil in May 2015.
The lack of any natural immunity in the Americas is thought to be helping the infection to spread rapidly.
Over 4,000 babies have been born with microcephaly in Brazil since October, and government officials in El Salvador have urged women to not get pregnant until 2018.
The C.D.C. is urging pregnant women to avoid travel to the 13 countries hardest-hit by the virus.