Last year, at an event in New York, I learned about an impressive woman whose story I want to share with you. Her name is Cacilda Fumo, she lives in Mozambique, and every year she helps save hundreds of lives—by reminding them they are not alone.

Mozambique has one of the highest HIV infection rates in the world. More than 1.6 million people—10 percent of the adult population—are living with HIV.

Cacilda was diagnosed with HIV in 2002. “When I first learned about it, I thought I would die,” she recalls. “I used to wake up early morning and check if I am alive or not.”

But then she started meeting other people living with HIV, and as their numbers grew so did her strength and her belief she would live. Cacilda was one of the first in Maputo to be open about her status. She started wearing a t-shirt emblazoned with a logo that reads: “HIV POSITIVE.”

At times, people rejected her because of her status. Many more in her community, however, admired her for her courage, helping her create an even larger circle of friends and supporters. They met every week, praying together, cooking together, and sharing their stories. Eventually, the group had about one hundred people, many of them receiving life-saving anti-retroviral treatment. Cacilda emerged as their leader.

About the same time, Mozambique’s Ministry of Health was struggling to improve the delivery of anti-retroviral treatment. While the program was successful in putting thousands of patients on treatment for the first time, medical staff were overburdened with caseloads. People on HIV treatment often walked miles to reach their clinic and waited in long lines to get care. Every year, about 30 percent of HIV patients dropped off their life-saving treatment.

Working with Doctors Without Borders, the government of Mozambique decided to try a new approach to simplify care to help keep more people on treatment. They started organizing small peer support groups for people on HIV treatment. The idea was simple. Make treatment easier by putting more control into the hands of the patients. A representative from each patient group could pick up all the drugs for the group each month, saving the rest of the group the hassle of going to the clinic. Members of the groups, known as Community antiretroviral therapy (ART) Groups or CAGs, would also support one another to ensure they were all staying on their treatment.

When the program reached Maputo, Cacilda was ready to join. She helped organize dozens of support groups from her network. Then she went one step further. She kept track of the groups, checking whether members were attending their meetings and taking their treatment. If someone fell off treatment, she took upon herself to locate them and find out what was wrong.

“We help people feel strong knowing they are not alone,” she says.

Some patients who stop treatment are addicted to alcohol and forget to take their treatment, she says. Some don’t understand how the treatment works and the stop taking their medication as soon as they feel better. Others get busy with their jobs and drift away.

Whatever the reason, Cacilda warns them of the dangers of stopping treatment and encourages them to restart. Her efforts to bring back residents of Maputo to treatment has become nearly full-time work. Most days residents of Maputo see Cacilda traveling on foot—which is remarkable because due to a childhood injury she uses crutches—through the dirty alleyways and crowded markets in search of people who have stopped treatment. She doesn’t give up until she finds them.

Cacilda’s persistence pays off—in lives saved. Cacilda estimates that she tracks down about 500 people every year and encourages them to resume their treatment.

That’s a remarkable achievement—one that proves how much difference one life can make in the world.