There is currently no vaccine or medicine to treat Zika, a mosquito-borne virus that has spread across roughly 30 countries and territories in the Americas.

The Virgin Islands, Barbados and Jamaica in the Caribbean are most vulnerable because they rely on tourism to support their economies, according to data from the World Travel and Tourism Council.

For example, the Virgin Islands welcome nearly one million tourists each year, supporting roughly 30% of jobs on the islands. The British islands in the group are most at risk -- travelers support about 86% of economic activity in the area.

The U.S. Virgin Islands, by comparison, are less exposed to a downturn in tourism because it accounts for 30% of GDP.