Since the first cases of Zika virus were reported in the Americas in May 2015, at least 21 countries and territories have documented instances of the mosquito-borne disease. Now the World Health Organization reports the virus is likely to spread to all but two areas — Canada and continental Chile — in North, Central and South America. With nearly 4,000 cases of the virus, Brazil has been the hardest hit. However, El Salvador has issued a warning, advising citizens to delay pregnancy until 2018.
Zika is linked to babies born with the neurological condition microcephaly, which can cause developmental delays and even be fatal. There is no vaccine or treatment for the virus. Cases have also been reported in France and New York, although the latter are believed to have been acquired outside of the U.S. The virus isn't spread through physical contact.
The 21 affected countries are those with the highest levels of the mosquitoes that carry the virus. Additionally, the CDC has issued an alert that pregnant women should considering postponing travel to Bolivia, Brazil, Cape Verde, Colombia, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Saint Martin, Surname, Samoa, Venezuela and Puerto Rico. For pregnant women who have recently traveled to any of these areas, the CDC recommends testing and monitoring for the virus.