NEW YORK • Climate change is poised to increase the spread of dengue fever, which is common in parts of the world with warmer climates like Brazil and India, a new study warns.
Worldwide each year, there are 100 million cases of dengue infections that are severe enough to cause symptoms, which may include fever, debilitating joint pain and internal bleeding.
There are an estimated 10,000 deaths from dengue, which is transmitted by Aedes mosquitoes that also spread Zika and chikungunya.
The study, published on Monday in the journal Nature Microbiology, found a likelihood for significant expansion of dengue in the south-eastern United States, coastal areas of China and Japan, as well as to inland regions of Australia.
Dr Oliver Brady, an assistant professor at the London School of Hygiene & Tropical Medicine and an author of the paper, said that the research predicts more people in the US will be at risk in coming years.
Globally, the study estimated that more than two billion additional people could be at risk for dengue in 2080 compared with in 2015 under a warming scenario roughly representative of the world's current emissions trajectory.
That increase largely comes from population growth in areas already at high risk for the disease, as well as the expansion of dengue's range.
To estimate the future spread of the disease, Dr Brady and his colleagues took data on mosquito behaviour and projections on urbanisation (one type of Aedes mosquito that spreads the disease is especially prevalent in cities) and combined them with three different climate scenarios to model what might happen in 2020, 2050 and 2080. Under all three scenarios, the spread of dengue increased.
But how much the world warms has a significant impact on the spread of the disease.
The research, Dr Brady said, "hints at the idea that if we do control emissions better, we could stop or at least limit this kind of spread".
Warming temperatures help expand dengue's range because, in part, as it gets warmer, mosquitoes can thrive in more places where they could not previously. Warming temperatures also shorten the time it takes a mosquito to become a biting adult and accelerate the time between when a mosquito picks up a disease and is able to pass it on.
Aedes aegypti is particularly concerning, because, while other mosquito species will bite whatever is convenient, the Aedes aegypti mosquito prefers to bite humans.
While there is a dengue fever vaccine, it is ineffective for most people. Treatment for the disease focuses on ensuring that the patient gets enough fluids, which can be difficult because of severe nausea and vomiting.
"For a healthy individual, dengue is an awful experience that you never forget," said Eastern Connecticut State University's associate professor Josh Idjadi, who contracted dengue fever in French Polynesia. "For infants and elderly and the infirm, they're the ones that are going to be at risk."