Some 25,000 delegates gathered in Washington this week for the 2012 International AIDS Conference. They did so at a moment of exceptional promise. Gains in AIDS treatment are remarkable — and continuing.

One of the saddest tragedies in the world is for people to die of AIDS when lifesaving medicines are available. Just a decade ago, that tragedy was playing out across Africa. Thanks to the generosity of the American people, this is no longer the case today.

Through the President's Emergency Plan for AIDS Relief (PEPFAR) and the Global Fund to Fight AIDS, Malaria and Tuberculosis — working with governments, faith-based and community organizations, and the private sector — treatment and prevention have advanced at an almost unimaginable pace. This month, the Joint United Nations Program on AIDS (UNAIDS) announced that 6.2 million people in sub-Saharan Africa are on lifesaving antiretroviral AIDS drugs — up from just 100,000 in 2003.

This is more than a vast statistic. It is a series of real people's names — those of nurses, doctors, civil servants, farmers, students, entrepreneurs, and parents who did not leave orphans behind. It is proof of what many in Africa call the Lazarus effect: Communities once given up for dead have been brought back to life, and millions of men, women, and children are alive to build their futures.

An important by-product of this effort has been an improvement in African health systems. PEPFAR and other programs have helped improve standards and infrastructure. This has raised an exciting prospect: extending the gains on AIDS to other diseases.

It is heart-wrenching to save a woman from AIDS only to watch her die of cervical cancer, which is more prevalent among women with HIV. So Laura and I, along with the Bush Institute and partners from the public and private sectors, started Pink Ribbon Red Ribbon to save women from breast and cervical cancer, two of the leading causes of cancer death in Africa. Like PEPFAR, the program depends on a broad alliance. The Bush Institute is working with the Obama administration, UNAIDS, Susan G. Komen for the Cure, and private-sector partners, and Secretary of State Hillary Clinton has been a consistent champion.

We launched Pink Ribbon Red Ribbon in Lusaka, Zambia, in December, and returned to Africa this month to expand it to Botswana. During our trip, Laura and I went back to Zambia and helped refurbish a women's health clinic in Kabwe, two hours north of the capital.

As soon as we cut the ribbon, the clinic started screening women who had lined up to be tested for cervical cancer. It was a joy to see the relief on the first patient's face when she left with a clean bill of health. And it is heartening that those with early signs of cancer will have access to treatment and a good chance of beating it.

During the past decade, millions of lives have been saved and changed by a global effort. It would be a sad and terrible thing if the world chose this moment to lose its focus and will.

National and local governments in Africa can provide more resources and funding, as Zambia is. But to continue the momentum in the fight against AIDS, America must continue to lead. Having seen the need and accepted the challenge, we can't turn our backs now.

Former President George W. Bush wrote this for the Washington Post.