Researchers estimate 18% of global dengue burden is attributable to climate change
Florida has the largest outbreak of locally acquired dengue fever in the continental United States in nearly a century, according to a report from Jessica Meszaros of NPR member station WUSF. More than 400 locally acquired cases have been reported across the country so far this year, almost entirely in Florida. The outbreak is linked to the death of an elderly woman and continues to spread, the report said.
Dengue spreads to people through infected mosquitoes. Symptoms include high fever, headache and body pain, which is how the illness earned its “break-bone fever” nickname. People typically contract the virus while traveling through continents where it is always present, such as South America, Asia or Africa.
This year’s outbreak began with travel, the report found. People infected during trips abroad brought the virus back to the United States and passed it on to mosquitoes here, seeding local transmission that has since produced hundreds of cases.
Eva Buckner, an insect scientist at the University of Florida, said the scale of the outbreak has no comparison in her experience. “I have not seen anything like this. It is very much unprecedented,” Buckner said. One factor, she said, is that dengue has been highly active around the world recently, which “allows multiple travel cases to occur in Florida.”
Florida already has the mosquito species capable of carrying dengue, Aedes aegypti. A long drought this year compounded the risk, Buckner said, because the species’ eggs survive dry conditions. “Aedes aegypti has drought-resistant eggs, and so it allowed some of the eggs to build up in the environment,” she said. When rain finally arrived in June, the accumulated eggs hatched simultaneously — just in time for a hot, humid summer in which the mosquitoes thrive.
Cases spiked in Tampa, the report found, because the area was not prepared to combat the tropical disease the way more southern Florida counties already do.
Erin Mordecai, an infectious disease researcher at Stanford University, co-authored a study published last year that found a warming climate can increase the number of dengue transmissions. “We estimate that about 18% of the global dengue burden is attributable to climate change that had already happened by 1995 to 2014, so not even including the last decade of warming,” Mordecai said.
Climate change increases the chance that temperatures reach 84 degrees in more places, conditions optimal for dengue transmission. That analysis covered 21 countries in Latin America and Asia, but Mordecai said researchers are currently studying the United States.
Weekly dengue cases in Florida are slowing, however, as cooler, drier air moves into the state, according to the report.