NEW YORK, NY, Weds. Dec. 18, 2019 NPR – Dengue fever has surged across the continent, from Mexico down to Chile and Argentina, with nearly 3 million cases reported. That’s more than 20% higher than the previous record in 2015, NPR reports indicate.
Over 2 million of the reported cases have been in Brazil. Countries in Central America, including Belize, Honduras and Nicaragua, are also among the hardest hit.
The reasons from the surge range from rain (or lack of it) to the Zika virus.
Leah Katzelnick, an epidemiologist at the University of California, Berkeley who works on dengue in Nicaragua, says climate definitely plays a role.
The Aedes aegypti species of mosquito, which can infect people with the virus, will lay eggs in any pool of clean water. After this year’s heavy rains in Latin America, “you’re just fighting against everything,” Katzelnick says. The mosquitoes will breed in a puddle on the lid of a trash barrel — or even discarded tires.
Raman Velayudhan, a mosquito specialist with the World Health Organization, agrees that climate conditions such as warmer temperatures, high humidity and abnormal rains have contributed to this year’s surge. But so does drought: “If you have less rainfall, people hoard water,” he says, which can create places where mosquitoes can breed.
A second probable reason for dengue’s surge in Latin America comes from another virus: Zika.
After Zika swept through Latin America in 2016, rates of dengue dropped to fewer than 600,000 cases per year in the two years following. That’s the lowest number in the decade.
Gabriela Paz-Bailey, senior epidemiologist at the Center for Disease Control and Prevention’s Dengue Branch in Puerto Rico, explains that Zika and dengue are closely related viruses. “It is possible that the Zika outbreak in the Americas provided some short-term protection against dengue,” she says.
Researchers think antibodies the immune system created to fight Zika also protect against dengue. But this immune system response fades after a few years — which may have primed 2019 for a big dengue surge.
