Last week, the 19th International AIDS Conference convened in Washington. The last time the meeting took place there was 25 years ago, and the mood was entirely different. In 1987, our scientific knowledge about this exploding epidemic was in its infancy. What has since been accomplished emboldened the organizers to make this year's conference theme "Turning the Tide Together." Indeed, there is a possible end to the AIDS pandemic.

The medical advances discussed at the meeting result from a 30-year scientific journey characterized by incremental progress in understanding HIV and how it causes disease, the development of treatments and prevention tools, the testing of these interventions in clinical trials, and implementation of the tools in communities worldwide. Interventions previously proved to work in controlled clinical trials are now -- over and over again -- proving effective outside the research setting, in the real world, in poor and rich communities alike. The pieces are coming together.

More than 8 million people in low- and middle-income countries are receiving lifesaving antiretroviral drugs. These medications averted 840,000 deaths in 2011 alone, one of the most extraordinary accomplishments in public health history.

Still, 9 million HIV-infected people who need therapy are not receiving it. In the United States, more than 1.1 million people are infected with HIV, and 20 percent are not aware of it. This group inadvertently transmits the vast majority of the approximately 50,000 new infections that occur annually in the United States. Researchers and health departments are pursuing new approaches to test people for HIV and to provide treatment and care, as well as the support that enables HIV-infected individuals to maximize benefits from medical and social services.

Besides their lifesaving role as treatment, antiretroviral drugs can prevent HIV infection. By significantly lowering virus levels, they dramatically reduce the risk that infected people will transmit HIV to sexual partners or, in the case of pregnant women, to their infants. This concept has been proved in rigorous clinical trials, and new data indicate that the results may be even stronger than earlier reports.

There is also evidence of real-world health benefits at the community, regional and national levels: As antiretroviral coverage has been scaled up, incidence of HIV infection has gone down. Treatment as prevention, if properly implemented and used along with condoms and other proven tools, will significantly slow the trajectory of the pandemic.

Studies have also shown that people at high risk of HIV infection can reduce that risk by taking an antiretroviral pill daily -- a method known as pre-exposure prophylaxis, or PrEP. As with many treatment and prevention tools, the effectiveness of PrEP is directly related to how well people adhere to the prescribed regimen, and behavioral factors must be addressed when rolling out any intervention. Biologically based and behaviorally based interventions are both needed.

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While major research challenges remain, notably in developing a vaccine and a cure for HIV, it became clear last week that science has given us the tools we need to dramatically change the course of the HIV/AIDS pandemic and ultimately end AIDS. Now these tools must be applied.

Ending the HIV pandemic is an enormous and multifaceted challenge. We know it is possible, yet it will not happen spontaneously. It will require a global commitment of countries, governments and communities to strengthen their health care systems and build the capacity to provide HIV treatment and prevention. We need donors and partners to continue their investments, and we need new donor organizations and countries to step up. We must enhance what works and eliminate what doesn't, overcome legal and political barriers, and remove the stigma associated with HIV.

The global community has a historic opportunity based on solid scientific evidence to end the AIDS pandemic, opening the door to an AIDS-free generation.

Anthony S. Fauci is director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health. This is from The Washington Post.