Anthony S. Fauci is director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health.

I was honored to deliver the opening scientific plenary lecture Monday at the 19th International AIDS Conference in Washington. The last time the meeting took place here 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” — and allowed me to speak of a possible end to the AIDS pandemic.

The medical advances discussed at this 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 these tools in communities worldwide. What stands out in my mind from this week’s presentations is that 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. As discussed at the conference, such efforts are underway here in Washington, in other U.S. cities with high HIV infection rates and in other countries. Lives are being saved.

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 this week we saw new data that the results may be even stronger than earlier reports. We also saw evidence of real-world public 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.

Another scientifically proven prevention approach is voluntary medical male circumcision, which reduces a heterosexual man’s risk of acquiring HIV by 50 to 60 percent, an effect that increases over time. We are seeing reductions in HIV incidence in settings in Africa where adult male circumcision is being scaled up as part of a comprehensive HIV prevention strategy.

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. The Food and Drug Administration recently approved a pill combining two antiretrovirals for certain high-risk groups to use as oral PrEP together with condoms and other prevention tools. Antiretrovirals for use at the genital mucosa also have shown promise as PrEP and, as discussed this week, are being tested in vaginal rings that need to be replaced just once a month. As with many treatment and prevention tools, the effectiveness of PrEP is directly related to how well people adhere to the prescribed regimen, underscoring that behavioral factors must be addressed when rolling out any intervention. Biologically based and behaviorally based interventions are both needed.

Major research challenges remain, notably in developing a vaccine and a cure for HIV. But even without a vaccine or a cure, it became clear this week that science has given us the tools we need to dramatically change the course of the HIV/AIDS pandemic and ultimately end AIDS. Any argument that this cannot be achieved because we do not have evidence-based tools is no longer valid. Science has given us the tools. Now they must be applied.

Ending the HIV pandemic is an enormous and multifaceted challenge, but 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 does not, 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.