Dengue Fever

Aedes aegypti mosquito feeding on human skin — Aedes aegypti, the mosquito that spreads dengue. (Wikimedia Commons / Muhammad Mahdi Karim, GFDL 1.2)

Dengue is the world's fastest-growing mosquito-borne disease — a flavivirus that infects an estimated 390 million people every year. Most recover, but the most severe cases turn into life-threatening hemorrhagic fever.

The disease

Dengue spreads through the bite of the Aedes aegypti mosquito, an urban-adapted species that breeds in small pools of standing water and feeds during daylight. Most people who catch the virus feel mild flu-like symptoms — fever, headache, muscle aches, rash — and recover. About one in twenty cases progress to severe dengue, with plasma leaking from blood vessels, internal bleeding, and the risk of organ failure.

Before 1970, dengue was a problem in just nine countries. Today it's endemic in more than a hundred, on every continent except Antarctica, and the WHO calls it the fastest-growing mosquito-borne disease in the world. Reported cases jumped tenfold between 2010 and 2019. With climate change pushing Aedes aegypti into new territory, that trend is accelerating — locally-acquired cases now appear in southern Europe and the southern United States.

Why it's hard to stop

Dengue isn't one virus but four — DENV-1 through DENV-4, all closely related. Catching one serotype gives lifelong immunity to that one, but only short protection against the others. Worse, the antibodies from a first infection can actually amplify a second infection by a different serotype, a phenomenon called antibody-dependent enhancement. It's what makes second infections more likely to turn severe — and why a dengue vaccine has been so hard to build.

Two vaccines now exist — Dengvaxia (approved 2016) and Qdenga (2022). Dengvaxia is given only to people who have already had dengue once, to avoid triggering ADE in those who haven't. There's no approved antiviral treatment for active infection; doctors can only manage symptoms and watch for warning signs.

Folding@home is using a combination of cheminformatics and machine learning, in close coordination with experimental colleagues, to develop new therapies for dengue.