Melinda and I admired Nelson Mandela, as the world did, for his courageous stand against apartheid. But we came to know him personally for a different reason: the fight against HIV/AIDS.

He was especially powerful in speaking out against stigma. In many countries, especially in the early years of the HIV epidemic, there was a lot of misinformation about how the virus was passed. Some people were afraid to touch a person with HIV.

President Mandela knew how damaging that was. He knew it made fighting the epidemic harder, and it wrecked the lives of people suffering from the disease. He also knew the stigma was just based on fear and ignorance. He thought he could make a difference by teaching people the facts.

This was something we talked about a lot every time we met: How could we fight stigma and spread reliable information about the disease?

You can see the power of his example in one of my favorite photographs ever. My dad went to visit him in South Africa along with President Jimmy Carter. President Mandela took them to a clinic that cared for infants born with HIV. As reporters and photographers looked on, he picked up one of the babies and held it in his arms. President Carter and my dad did the same. The next day, the image of all three men cradling HIV-positive babies was broadcast throughout South Africa.

It sent a powerful message: that people did not need to be afraid of touching a person with HIV.

It was just one small step, and we still have a long way to go in the fight against AIDS. But Nelson Mandela played a crucial role in the progress we have made so far. I will never forget the example that he set.