Over the past two years, the phrase “HIV cure” has flashed repeatedly across newspaper headlines. In March 2013, doctors from Mississippi reported that the disease had vanished in a toddler who was infected at birth. Four months later, researchers in Boston reported a similar finding in two previously HIV-positive men. All three were no longer required to take any drug treatments. The media heralded the breakthrough, and there was anxious optimism among HIV researchers. Millions of dollars of grant funds were earmarked to bring this work to more patients. But in December 2013, the optimism evaporated. HIV had returned in both of the Boston men. Then, just this summer, researchers announced the same grim results for the child from Mississippi. The inevitable questions mounted from the baffled public. Will there ever be a cure for this disease? As a scientist researching HIV/AIDS, I can tell you there’s no straightforward answer. HIV is a notoriously tricky virus, one that’s eluded promising treatments before. But perhaps just as problematic is the word “cure” itself. Science has its fair share of trigger words. Biologists prickle at the words “vegetable” and “fruit”—culinary terms which are used without a botanical basis—chemists wrinkle their noses at “chemical free,” and physicists dislike calling “centrifugal” a force—it’s not; it only feels like one. If you ask an HIV researcher about a cure for the disease, you’ll almost certainly be chastised. What makes “cure” such a heated word? HIV hijacks the body's immune system by attacking T cells. It all started with a promise. In the early 1980s, doctors and public health officials noticed large clusters of previously healthy people whose immune systems were completely failing. The new condition became known as AIDS, for “acquired immunodeficiency syndrome.” A few years later, in 1984, researchers discovered the cause—the human immunodeficiency virus, now known commonly as HIV. On the day this breakthrough was announced, health officials assured the public that a vaccine to protect against the dreaded infection was only two years away. Yet here we are, 30 years later, and there’s still no vaccine. This turned out to be the first of many overzealous predictions about controlling the HIV epidemic or curing infected patients. The progression from HIV infection to AIDS and eventual death occurs in over 99% of untreated cases—making it more deadly than Ebola or the plague. Despite being identified only a few decades ago, AIDS has already killed 25 million people and currently infects another 35 million, and the World Health Organization lists it as the sixth leading cause of death worldwide. HIV disrupts the body’s natural disease-fighting mechanisms, which makes it particularly deadly and complicates efforts to develop a vaccine against it. Like all viruses, HIV gets inside individual cells in the body and highjacks their machinery to make thousands of copies of itself. HIV replication is especially hard for the body to control because the white blood cells it infects, and eventually kills, are a critical part of the immune system. Additionally, when HIV copies its genes, it does so sloppily. This causes it to quickly mutate into many different strains. As a result, the virus easily outwits the body’s immune defenses, eventually throwing the immune system into disarray. That gives other obscure or otherwise innocuous infections a chance to flourish in the body—a defining feature of AIDS. Early Hope In 1987, the FDA approved AZT as the first drug to treat HIV. With only two years between when the drug was identified in the lab and when it was available for doctors to prescribe, it was—and remains—the fastest approval process in the history of the FDA. AZT was widely heralded as a breakthrough. But as the movie The Dallas Buyer’s Club poignantly retells, AZT was not the miracle drug many hoped. Early prescriptions often elicited toxic side-effects and