In which countries in the americas do i have to worry about zika virus from mosquito bites?

CDC website: Comprehensive, reliable information is available from the Centers for Disease Control and Prevention: http://www.cdc.gov/zika/index.html/

22 countries:: As of Jan 27, 2016, these countries have Zika virus transmission in the Americas: Barbados Bolivia Brazil Colombia Dominican Republic Ecuador El Salvador French Guiana Guadeloupe Guatemala Guyana Haiti Honduras Martinique Mexico Panama Paraguay Puerto Rico Saint Martin Suriname U.S. Virgin Islands Venezuela

CDC website: Visit the Center for Disease Control and Prevention (CDC) website for a complete updated list of countries to which to avoid travel. http://www.cdc.gov/zika/

So far in 2015...: Zika transmission areas in North and Central America in 2015: El Salvador, Guatemala, Honduras, and Panama in Central America; plus in Mexico. Zika in South America and the Caribbean: Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname, and Venezuela; plus Barbados, Guadeloupe, Haiti, Martinique, Puerto Rico, and Saint Martin.

In 2017---: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, Panama, Mexico, Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, Venezuela. This does not include the Caribbean. See: https://wwwnc.cdc.gov/travel/page/zika-travel-information