Dengue—a virus most commonly transmitted by the Aedes aegypti mosquito—infects some 400 million people yearly.
It causes high fever, severe headaches, vomiting, and sometimes death. About 40 percent of the world’s population is at risk, and as the climate warms and travel increases, that risk will only climb.
This year, the World Health Organization started recommending the first vaccine to prevent dengue, and inoculations have begun in hot zones like Brazil and the Philippines.
Four viruses cause dengue, so developing a vaccine that protects against all four took researchers 20 years to do. If 20 percent of the population gets vaccinated, dengue cases could drop 50 percent within five years.
Controlling dengue could also reduce the $9 billion the disease costs global economies each year.