Three and a half decades into the global HIV pandemic, it may seem strange the world still needs one special day to remind us about the terrible toll of the disease. This World AIDS Day, on Tuesday, should also be a reminder we have the tools to end the AIDS epidemic. But do we have the will to do it?

This 25th World AIDS Day comes at a time of unprecedented optimism the end is in sight of HIV as a global public health threat. Scientific breakthroughs have proven that immediate treatment for HIV can improve health and prevent transmission, and that antiretroviral drugs can protect uninfected people from becoming infected. An accelerated pace of treatment has provided lifesaving medicines to 15 million people living with HIV today. The number of people dying from HIV-related causes began to decline in the last decade, and new infections have fallen 13 percent in the last three years.

All that progress is enough to make many think the end is near. Yet much remains to be done. We are not close to ending AIDS, but we are at the beginning of the end.

The 15 million now receiving antiretroviral treatment represent less than half of the estimated 37 million people living with HIV, all of whom need treatment. And with mortality rates dropping while new infections continue, the number of people living with HIV is increasing. In most of the world, weak, understaffed health care systems are struggling to manage their patients’ care, and they face providing treatment for millions more.

Still, funding to respond to HIV through the President’s Emergency Plan for AIDS Relief and the Global Fund to Fight AIDS, Tuberculosis and Malaria has been flat for the last several years. Recently, Sen. William Cassidy, R-La., urged cuts in funding for HIV research. These approaches, in the long run, will not leave us where we are now — with an ongoing, expensive and deadly pandemic — but will result in sliding back from the advances that have been made. To reach the number of people necessary to turn the trajectory of the epidemic, we need to do a better job of doing what we already know works, and invest more to get the tools we need.

We can see this clearly in the United States, where just 30 percent of the 1.2 million people living with HIV are treated effectively enough to suppress their virus, protect their health and prevent transmission, and where 50,000 people are newly infected with HIV every year. Rural Indiana recently experienced an outbreak of HIV among persons who inject prescription drugs. And while HIV infections have declined in many cities previously significantly impacted by the epidemic, like San Francisco and Washington, D.C., sadly, that is not the case locally. Georgia is the nation’s No. 2 state, and Atlanta, the fifth metropolitan area, for new HIV diagnoses.

We can, and should, do better. It is imperative we continue to re-engineer the health care system to improve patient outcomes. The Ryan White Program, which began 25 years ago to ensure health care and essential support services for people living with HIV in the United States, must be fully funded to meet existing needs. At the same time, proven prevention measures — including syringe exchange programs that protect public health by averting transmission from injected drug use — should be supported. We should not allow a local outbreak similar to what occurred in Indiana.

Worldwide, the rights of people whose circumstances put them at greatest risk for infections – sexual minorities, prisoners, young women and girls among them — must be protected. And if we are to feel secure in the gains we make, we need to ensure together that health systems are ready to confront their next challenges as well as the ones they face now.

Even then, it remains unlikely treatment alone will be powerful enough to stop transmission. With the knowledge that while HIV no longer needs to be a death sentence, it continues to be a life sentence, research towards long-acting treatments, a cure and a vaccine must continue.

This World AIDS Day would be a tempting time to celebrate the progress made. But as long as the global HIV pandemic continues, World AIDS Day is a time to look ahead and strengthen our resolve to end it.

Dr. Carlos del Rio is chairman of the HIV Medicine Association, chairman of the Department of Global Health at the Rollins School of Public Health, and professor of medicine in the Division of Infectious Diseases at Emory University School of Medicine.