This week, global leaders gather in Washington, D.C., for the 19th International AIDS Conference, marking the first time since 1990 that the conference is being held in the United States.

It is remarkable that in these last two decades we have moved from a frightening and unknown killer, to a horrifying global epidemic causing millions of deaths annually, and now having an AIDS-free generation within reach.

What’s perhaps more striking is the unlikely group that contributed a crucial component to this success. Two decades ago, no one would have predicted that Christians would so quickly change their response to the HIV and AIDS epidemic from criticism to compassion.

I experienced my own about face on this issue in 1998 when I visited the epicenter of the AIDS crisis in Uganda. I’ll never forget the day I met a boy named Richard who had become the head of his household in Uganda’s Rakai district. Richard was 13 years old and taking care of his two younger brothers. Two crude piles of stones just outside the door of his hut marked the graves of Richard’s parents.

Having just left my job as president of Lenox in order to work for World Vision, I was overcome both with the enormity of the devastation — especially on children — and World Vision’s meager response. The lack of response by Christians also angered me. Why weren’t God’s people caring for the widows and orphans created by AIDS?

Upon my return from Uganda, World Vision launched a campaign to engage Christians in the global fight against HIV and AIDS. At the time, an internal World Vision survey found that only 3 percent of Christians said they would help children who were affected by HIV and AIDS. Against such opposition, our efforts would have had little effect if God wasn’t working throughout Christian churches. Christian colleges and their students campaigned on the issue. Kay and Rick Warren also had their own personal encounters with those suffering because of HIV and AIDS. The tide was finally beginning to turn.

Christians also played an important role in gathering support for President Bush’s President’s Emergency Plan for AIDS Relief (PEPFAR) program established in 2003, which spent nearly $6 billion in 2012 on HIV and AIDS prevention and care, the largest effort of any government focused on a single disease. This initiative is literally saving millions of lives. By 2010, nearly 4 million people received drug treatment, and 13 million people, including 4 million orphans and vulnerable children, received support and care.

Though the world has turned an important corner towards being AIDS-free, 34 million people still live with the disease and 17 million children have been orphaned because of it, according to recent UNAIDS and UNICEF reports. While defeating AIDS is within our grasp, there is still much work to be done.

●At current rates, we will not meet the Millennium Development Goal of providing universal drug coverage for those with AIDS by 2015.

●The latest UNAIDS report states that only 18 percent of children with AIDS receive the therapy they need.

●Much more work needs to be done to prevent mother-to-child transmission of HIV.

●PEPFAR funding is at its lowest level since 2007.

A decade ago, more than half of Christians surveyed by World Vision said that they would probably or definitely not help children orphaned by AIDS. However, today, Christians are proving by their actions that the tide has turned in their willingness to help bring an end to HIV and AIDS.

As thousands gather for the International AIDS Conference this week, with the end of AIDS in sight, let’s focus on our role and responsibility as Christians in continuing this important work until we truly achieve an AIDS-free generation.

Richard Stearns is president of World Vision US and author of “The Hole in Our Gospel.” Follow Stearns on Twitter @RichSteans.