Story highlights Former President George W. Bush is in Zambia with his wife, Laura

They have helped renovate a cancer screening clinic there

Bush: "I believe strongly that with power and wealth comes a duty to serve the least"

" I did what I did; I know the spirit in which I did it," says Bush of his legacy

Former President George W. Bush has a new mission: helping those with the least in Africa.

He has stayed largely out of the limelight since his second term as U.S. president ended in 2008.

But on another continent, thousands of miles from the politics and infighting of Washington, Bush is quietly burnishing a humanitarian legacy that may in some people's eyes outweigh the controversies sparked by his time in office.

He and his wife, Laura , are in Africa this week, where they helped renovate a cancer screening clinic in Zambia.

The clinic, which is designed help women fight cervical cancer, builds on the former president's work fighting HIV/AIDS on the continent.

While he was in office, Bush set up a plan -- the President's Emergency Program for AIDS Relief -- that made a massive investment in antiretroviral drugs and dramatically reduced the number of AIDS deaths in Africa.

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"I'm really proud of the American people for their generosity," he told CNN in an exclusive interview. "I wish Americans knew how many lives were saved. Someday, they will."

Bush got his own hands dirty working on the refurbishment of the clinic -- a sign, he said, of his commitment to the cause.

Photos: Photos: Bushes renovate Zambian clinic Photos: Photos: Bushes renovate Zambian clinic Bushes renovate Zambian clinic – For two days, former President George W. Bush and first lady Laura Bush worked alongside Zambians, U.S. embassy officials and the Bush Institute staff to renovate the Mosi Oa Tuny Clinic. It will serve as a cervical cancer screening and treatment center in Livingstone, Zambia, continuing the global health initiative at the George W. Bush Institute. Above, Bush does some touch-up work. Click through the gallery for more pictures from their June 29-30 visit: Hide Caption 1 of 8 Photos: Photos: Bushes renovate Zambian clinic Bushes renovate Zambian clinic – This is the second time the Bushes came to Zambia on a health mission. Last July, they renovated and opened the NguNgu Health Center in Kabwe, Zambia. Hide Caption 2 of 8 Photos: Photos: Bushes renovate Zambian clinic Bushes renovate Zambian clinic – Bush visits the Cathedral of St. Theresa Catholic Church in Livingstone. Hide Caption 3 of 8 Photos: Photos: Bushes renovate Zambian clinic Bushes renovate Zambian clinic – The project is in direct support of the Pink Ribbon Red Ribbon partnership, which combats cervical and breast cancer in the developing world. It's spearheaded by the Bush Institute, PEPFAR, UNAIDS and Susan G. Komen for the Cure, along with other private and public partners. Hide Caption 4 of 8 Photos: Photos: Bushes renovate Zambian clinic Bushes renovate Zambian clinic – The clinic in Livingstone was scheduled to open to the public on Monday, July 1. Hide Caption 5 of 8 Photos: Photos: Bushes renovate Zambian clinic Bushes renovate Zambian clinic – Laura Bush pauses at the Mosi Oa Tuny Clinic. Hide Caption 6 of 8 Photos: Photos: Bushes renovate Zambian clinic Bushes renovate Zambian clinic – George W. Bush does some painting during renovations. Hide Caption 7 of 8 Photos: Photos: Bushes renovate Zambian clinic Bushes renovate Zambian clinic – After their trip to Zambia, the Bushes will travel to Dar es Salaam, Tanzania, to host the Bush Institute's African First Ladies Summit. The theme is "Investing in Women: Strengthening Africa." Hide Caption 8 of 8

"I'm here to serve and I believe strongly that with power and wealth comes a duty to serve the least," he said.

"Our purpose is to elevate the need for screening for cervical cancer throughout the continent of Africa."

The renovated clinic opened Monday as a cervical cancer screening and treatment center, and the Bushes hope it will help save the lives of thousands of women.

"It breaks your heart to realize that such hope was given to communities throughout the continent of Africa because of antiretrovirals and then women are dying of cervical cancer -- so there's hope and then there's despondency," George Bush said.

"We wanted to help make sure that despondency didn't settle in."

Bush at his best

Bush's harshest critics might be surprised by this side of the former president.

His shirt splattered with paint from the project, he appeared genuinely happy about doing manual labor. He was joking, jovial and genuinely happy to be there.

Bush was relaxed as he spoke with CNN, saying that after an extended period out of the limelight he feels like a tortoise sticking its head out of its shell.

The former president is aware that his legacy will be tied to the Iraq War, but he wants people to know what he is doing in Africa, too.

'History will judge'

In his comments, Bush also touched on the subject of Nelson Mandela, who is on life support in a South African hospital.

"Sometimes, there are leaders who come and go. His legacy will last for a long time," he said of the ailing anti-apartheid icon.

Mandela had criticized him publicly about the war in Iraq, Bush said he doesn't bear a grudge.

"He wasn't the only guy," he said. "It's OK. I made decisions that were the right decisions. History will ultimately judge. I never held someone's opinion against him; I didn't look at him differently because he didn't agree with me on an issue."

Bush also initially said he wasn't bothered about his ratings in opinion polls, even if some of them now put him at a similar level to Obama.

"The only time I really cared was on Election Day," he said.

Then, drawing laughter from his wife, he checked himself and said, "You know, I guess it's nice. I mean, let me rephrase that: Thank you for bringing it up."

In any case, the former president said he doesn't expect a fair assessment of his legacy in his lifetime.

"I won't be around, because it will take a while for the objective historians to show up," he said. "So I'm pretty comfortable with it. I did what I did; I know the spirit in which I did it."