Patrick Strudwick talks to Francoise Barre-Sinoussi about how she identified HIV as the cause of AIDS, and her Nobel Prize. In the early, frantic confusion of the AIDS crisis, as doctors and patients scrabbled for answers, desperate to grasp what was smothering the immune systems of the young and fit, there was, in 1983, a turning point, a pivot on which the rest of the pandemic would hinge: the discovery of HIV. When Françoise Barré-Sinoussi with her colleague Luc Montagnier found the virus that causes the disease, it proved monumental - a boulder thrown into a lake whose ripples still fan out today.