New NRDC analysis finds that two types of mosquitoes capable of transmitting dengue fever can now be found across at least 28 states. As temperatures rise, the potential for transmission of this dangerous disease may increase in vulnerable parts of the United States as warmer temperatures and changing rainfall conditions expand both the area suitable for the mosquito vectors and the length of the transmission season. An estimated 173.5 million Americans live in counties with one or both of the mosquito species that can transmit dengue fever.