Dengue expert and Northeastern University Professor Michael Johansson has said it is unclear whether the outbreak is one sustained chain or “multiple smaller introductions.” One chain would mean Tampa kept the virus’s reproduction number above one for months.

Especially in South Florida, there are now many Aedes aegypti mosquitoes , says Michael Johansson, an epidemiologist at Northeastern University.

Seasonal outbreaks of the disease, which affects up to 400 million people worldwide But this time is a little different, says Michael Johansson, an epidemiologist at Northeastern University. “This is the most locally acquired cases that we’ve seen in the state,” he says.