How dengue makes the immune system the enemy

Aedes aegypti mosquito. Photo: iStock / Oistock89

When someone gets sick, their body learns what the virus looks like, and destroys it upon re-infection. But when someone is infected with dengue a second time, the immune system appears to help the virus cause a more severe and fatal illness. Previously only seen in the lab, a new study published Thursday in the journal Science shows a direct link between the dengue antibodies themselves and severe illness in humans, supporting a 40-year-old theory.

Why it matters: Dengue fever infects as many as 390 million people each year, up to 96 million of whom will experience symptoms. For most, access to medical treatment makes dengue survivable. But for a small fraction of victims, the virus can progress from a normal infection to a life-threatening hemorrhagic illness in less than a day. A better understanding of how and why this happens could save thousands of lives.