I used to keep a picture on my desk, taken on Castro Street, in 1983, at the moment when it seemed as if gay life in San Francisco was ending forever. There were two men in the photograph: the first, tall and gaunt, was leaning over the other, who was in a wheelchair, tucking a blanket around what little was left of the wasted man. A friend had given me the picture just before I began covering the AIDS epidemic for the Washington Post, along with a message. “Don’t forget these people when you write this story,” he told me. “This is not about policies. It’s about being human.” My friend died a few months later—nearly three decades ago. I must have spent a thousand hours staring at that photograph during the years since then, enough time to memorize the deep sadness in the hollow black eyes of both men.

I have covered wars, before the epidemic began and since. They are all ugly and painful and unjust, but for me, nothing has matched the dread I felt while walking through the Castro, the Village, or Dupont Circle at the height of the AIDS epidemic. It could seem as if a neutron bomb had exploded: the buildings stood; cars were parked along the roadside; there were newsstands and shops and planes flying overhead. But the people on the street were dying. The Castro was lined with thirty-year-old men who walked, when they could, with canes or by leaning on the arms of their slightly healthier lovers and friends. Wheelchairs filled the sidewalks. San Francisco had become a city of cadavers.

In 2002, while writing a Profile of Larry Kramer, the dark prophet of the American AIDS epidemic, I spoke to Tony Kushner, who received a Pulitzer Prize for his brilliant play about that time, “Angels in America.” He told me what those days did to him. “I had just started coming out of the closet, and gay life had seemed so exciting,’’ he said. But by the time he had finished reading Kramer’s shocking article “1,112 and Counting,’’ which appeared in 1983 in the New York Native and demanded that gay men start to take notice of the catastrophe they faced, Kushner realized that “we were confronted with a genuine plague. People were beginning to drop dead all around us, and we were pretending it was nothing too serious.”

Kramer and many other activists changed all that. Outrage and new medicines largely overcame denial and hatred. In the years that followed, the epidemic seemed to go away—though of course it never did, here or anywhere else. (By the end of this year, AIDS will have killed nearly forty million people—most of them in Africa.) And this week, in a powerful story in the Times, Donald McNeil pointed out that those most wretched days could return. “Federal health officials are reporting a sharp increase in unprotected sex among gay Americans,’’ he wrote, “a development that makes it harder to fight the AIDS epidemic.”

That is a genteel way to put it. Thomas R. Frieden, the director of the Centers for Disease Control and Prevention, was a bit more frank. “Unprotected anal intercourse is in a league of its own as far as risk is concerned,’’ he said. Three decades of data demonstrate the truth of that statement. If unprotected anal intercourse is rising among gay men—a trend noted not just in America but in much of the Western world—the rates of HIV infection will surely follow.

Why is this happening? Put at least some of it down to human nature. Why do people refuse to vaccinate their children against measles or whooping cough? In many cases, because they have never seen measles and have no idea what it might do. (For perspective, more than a hundred and fifty thousand people died of measles in the developing world last year.) HIV is far more dangerous than measles, but also much more complicated. HIV is tied up with sex, a basic human need, but also with desire, shame, discrimination, and fear. What twenty-year-old man, enjoying his first moments of sexual adventure, is going to be scared because, ten years before he was born, people like me saw gay men writhe and vomit and die on the streets where he now stands? For a while, in the nineties, gay men were scared, and the statistics showed it. They used condoms regularly, and tested themselves to see if they were infected. Many still do, but others began to weary long ago of the sexual and emotional straitjacket. A drug like crystal meth (which erases inhibitions and greatly enhances sexual pleasure), while addictive and attractive, also presented an obvious and immediate drawback: it caused a condition known as “crystal dick”—no erection, no sex. Then people began to combine crystal with Viagra, and a new surge of infections began.

Can we halt this epidemic once again? Of course, or at least the dangers can be greatly reduced. But of the more than a million Americans who are infected with HIV (there are fifty thousand new cases a year), many have no decent health care, and nearly a third are not even aware they are infected. Racism, homophobia, and poverty continue to drive much of the epidemic. Minorities have the highest infection levels and are least likely to have access to satisfactory medical attention or drug treatments. Obamacare will help, but how fast or how well, nobody yet knows. This should be repulsive to us all; those people need education immediately, but there is little public funding available to teach young gay African-American men how to have sex with each other safely. That’s the society we seem to have become.

The only appropriate conclusion here is to listen, again, to Larry Kramer’s warning. What was true in 1983 may well become true again. “If this article doesn’t scare the shit out of you,’’ he wrote in “1,112 and Counting,” “we are in real trouble. If this article doesn’t rouse you to anger, fury, rage and action, gay men have no future on this earth. Our continued existence depends on just how angry you can get… Unless we fight for our lives we shall die.”

Photograph by Sean Gallup/Getty.