Patti Sprague is playing the world's longest game of hide and seek.
Traversing fences, shimmying under houses and tramping through the leafy, lush backyards of Florida's Key West, Sprague has one target: mosquitoes. Sprague has been an inspector with the Florida Keys Mosquito Control District since 2011, where she's on the front lines of a battle against one of the world's deadliest creatures.
The mosquitoes in the Keys are mainly just a nuisance, except for one kind: Aedes aegypti, a non-native species that carries maladies including dengue fever and chikungunya. Typically tropical diseases, dengue and chikungunya infect as many as 400 million people worldwide; dengue alone has surged 30-fold in the last 50 years, according to the World Health Organization. And with climate change and increased travel and trade, it's posing threats even in areas where it was thought to be wiped out, including the U.S.'s southernmost points.
"Dengue is kind of this sleeper disease; It can exist in these low levels without us even knowing it, and then flare up," entomologist Michael Doyle, director of the Florida Keys Mosquito Control District, said in an interview. "We want a structure in place, so five years down the road, if there is dengue coming into the Keys in large numbers, we won't have the mosquitoes to spread anything."
Dengue's usually not fatal, though its effects can sometimes be so painful the malady has been dubbed "breakbone fever." It hospitalizes 500,000 people each year, sometimes overwhelming hospitals in developing countries. And in its severest forms, it does kill: dengue is responsible for 22,000 deaths annually, mostly in children, according to the WHO.