Florida’s current dengue outbreak appears to be the largest in several decades in the continental United States.

State health officials reported this week that more than 250 locally acquired cases of the mosquito-borne disease have been tallied so far this year. The vast majority of them were in Hillsborough County, home to Tampa.

Federal health officials say their data on dengue outbreaks is limited. But available information from state health departments and medical journals suggests the Florida outbreak marks the most cases in a calendar year for any state since at least the 1940s.