Dengue is a viral infection that can be pretty benign; you get a fever, a headache, maybe some pain, and you’re out of commission for a few days. It can also be just awful, according to the U.S. Centers for Disease Control and Prevention: severe headache, pain behind the eyes, a rash, bleeding gums or nose. With no known cure other than “drink lots of fluids and wait it out” and a propensity to put people in the hospital, dengue hemorrhagic fever can be a definite threat to people’s well-being.
The mosquito-borne viruses that cause dengue fever had—as of the 1950s—a pretty small range, says The New York Times. Since then, however, the disease has been expanding at a rapid clip, with the World Health Organization saying that 40% of humans are now at risk.
Particularly hard hit, says the Times, has been India. The official count says 30,002 people got the disease between January and October of this year, a massive bounce over last year’s total. That number, though, may be a drastic underestimate.
“I’d conservatively estimate that there are 37 million dengue infections occurring every year in India, and maybe 227,500 hospitalizations,” said Dr. Scott Halstead, a tropical disease expert focused on dengue research.
The problem has gotten so bad that at the current pace, pretty much everyone born in the country will get dengue by the time they’re an adult. It also makes for a pretty convincing discouragement to tourism:
For those who arrive in India as adults, “you have a reasonable expectation of getting dengue after a few months,” said Dr. Joseph M. Vinetz, a professor at the University of California at San Diego. “If you stay for a longer period, it’s a certainty.”
With climate change likely to affect temperature and precipitation patterns worldwide, experts are worried that the range of the mosquitoes that vary the dengue viruses, and hence the disease itself, will expand. The Times says that efforts to create a vaccine against the disease have so far been disappointing. The best bet for India, all the other countries afflicted by dengue, and those where it may be soon, is to make sure that the health care systems are robust enough to deal with patients who need care.
More from Smithsonian.com:
How Mosquitos Are Out-Smarting Humans