While you were worrying about rising sea levels…

Original Reporting | By David Noriega |

Sept. 25, 2013 — The future consequences of climate change in Florida have often been envisioned in terms of rising sea levels and erratic weather: flooded coastal cities, violent hurricanes, critical infrastructure made to malfunction by invading seawater.

“Why would Mrs. Nicholson want to go to Florida in the winter and get dengue? She probably wouldn’t.” — Robert Repetto, International Institute of Sustainable Development

But an ongoing outbreak of dengue fever in Martin and St. Lucie counties, on the state’s Atlantic coast, may provide early warning of an under-appreciated threat: as Florida’s environment becomes more conducive to the spread of mosquitoes, the state’s residents could be at greater risk for contracting a variety of diseases. 

As with every other aspect of climate change, increased incidence of disease could carry potentially huge economic consequences. Remapping Debate focused its inquiries on a seldom-discussed but critical one: we asked what increasing outbreaks of illness would mean for real estate markets. The economists and other experts we interviewed agreed that property values would almost certainly suffer because fears of illness would deflate demand for Florida real estate.

The state’s trajectory need not be one of gloom and doom. But the rise of a climate-facilitated mosquito threat, Remapping Debate found, means that the decisions Florida makes about the strength of its public health and other health care infrastructure will become ever more important to whether the threat can be effectively met.

Some worry, however, that the current response is not encouraging: “We’re arguably regressing at a time when we need to be reacting to what may very well be a public health crisis,” said Democratic State Representative Mark S. Pafford.


The outbreaks so far

The Aedes aegypti mosquito, the most common carrier of dengue, breeds in small containers of water. After it rains, anything from a discarded bottle cap to a garden bromeliad can become a cradle for dozens of larvae. And since the current outbreak of dengue began five weeks ago in Martin County, some 40 miles north of Palm Beach, rain has come unseasonably heavy and late.

“We generally don’t get the kind of rain we’re getting right now in September,” said Gene Lemire, manager of mosquito control for Martin County. September is usually a slow month for mosquito control, but not this year. “I’ve got all kinds of water on the ground, so I’ve got all kinds of breeding sites,” Lemire said. To make matters worse, the air is still warm. “As long as you’ve got moisture coinciding with warm weather, you have mosquito breeding.”

The Martin County dengue outbreak, which so far has infected 20 people, is the second in Florida since an outbreak in Key West in 2009, which was the first time dengue was found in Florida in nearly 60 years.


Prospects for the future

While any climate scientist would caution against making inferences on long-term climate patterns based on individual weather events, those we interviewed confirmed that Martin County’s protracted rainy season nevertheless matches up with a likely future: longer and wetter summers with shorter and milder winters mean less opportunity for mosquitoes to die off as the weather grows cooler and drier, which in turn translates to an increased risk of exposure to vectors — organisms that carry disease, in this case mosquitoes.

“Vector abundance is extremely important in all calculations of risk of infection,” said Nathan Burkett-Cadena, a mosquito biologist at the University of South Florida. “I would say milder winters are definitely going to result in larger mosquito populations subsequent summer, and that’s going to drive transmission of vector-borne diseases.”

How does dengue feel?

Dengue is colloquially known as “breakbone fever” for the excruciating joint and muscle pain it causes. It can also lead to sudden-onset fever, headaches, and a rash.

Dengue has four strains, or serotypes, with different symptoms of varying intensity. This complicates the question of immunity. If people get infected with one strain of dengue, they will likely be immune to further infections from that strain. But if they are then infected with a different strain, the possibility of severe or fatal illness — with symptoms like intense fever, internal bleeding, and shock — increases.

“So, if you have multiple serotypes of dengue virus circulating in any area, it’s an extreme problem,” said Nathan Burkett-Cadena, a researcher at the University of South Florida.

This unusual interaction has stymied the development of effective vaccine: immunizing people to a particular strain of dengue only makes them more vulnerable should they contract another, and a vaccine covering all four strains has yet to be invented.

The types of mosquitoes that could proliferate and spread around Florida are also vectors for different kinds of encephalitis, or swelling of the brain. Typical symptoms include fever, malaise, and joint and muscle pain. Many cases are fatal. Some of these diseases, like Eastern equine encephalitis and St. Louis encephalitis, are already present in Florida. Others, like Venezuelan equine encephalitis, are present in countries further south and, scientists warn, may spread northward.

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