The quick and seemingly inexplicable death of 20-year-old Brazilian model Mariana Bridi da Costa brought the dangers of sepsis—the body's inflammatory reaction to an infection—into focus, CNN reports. It can start with something as simple as a skin wound or, as in da Costa's case, a urinary tract infection. Most times, the body heals itself, but symptoms of danger include fever, a shift in blood pressure, rapid breathing, and confusion.
Da Costa's case is especially rare because she was young and healthy. The Mayo Clinic sees about 100 such cases a year, with a 75% survival rate. "You can ask, 'Why her?' but really no one knows why her," says one specialist. "It might have something to do with her immune system. It might be about her genetics." Muppets creator Jim Henson died of sepsis, which began as pneumonia, at age 53.
(Read more urinary tract infection stories.)