Outbreaks of chikungunya virus occurred primarily in Africa, Asia, the Indian and Pacific oceans, and Europe. In 2013, chikungunya virus was identified in local transmission in the Caribbean countries and territories. It has since spread throughout the Americas where 1.7 million cases have been reported.
The greatest risk is from spread to new areas by travelers who visited areas with ongoing epidemics. The mosquitoes that carry the virus are the same ones that spread dengue and Zika viruses (Aedes eagypti and Ae. albopictus). Because those people who are infected have a high viral load, local transmission is possible wherever the mosquitoes live. Most epidemics occur in tropical areas in the rainy season, but they can also occur less frequently in drought conditions.
Chikungunya 2018 map of countries where cases have been reported. Courtesy of CDC.