A woman planning a Florida vacation in Key West called the health department there last week to ask if it were true that the city was being evacuated because of an epidemic of dengue fever.

“No!” Chris Tittel, a spokesman for the Monroe County Health Department, says he told her. “No, no, no, no, no.”

Dengue (pronounced DENG-gay) is a viral illness, spread by mosquitoes, that can cause fever, headaches, body aches and a rash. Symptoms range from mild to severe, although some people have no symptoms.

Without a doubt, there is dengue in Key West, though at 27 known cases last year and 18 so far this year, it is hardly what most people would call an epidemic. But those cases are the first outbreak in Florida since 1934, and some medical experts fear that the disease, once rampant on the Eastern Seaboard, could take hold again.