In tweets, songs, telephone calls, cards and more, messages of love have come from across South Africa and the world for 94-year-old Nelson Mandela, giving the family comfort and hope as he remains hospitalized in serious condition with a lung infection, his wife said Monday. As the anti-apartheid hero spent a 10th day in the hospital, Graca Machel expressed the family's gratitude for the support "from South Africans, Africans across the continent, and thousands more from across the world ... to lighten the burden of anxiety; bringing us love, comfort and hope. " Machel has already experienced the loss of a husband. Mozambican President Samora Machel, her first husband, died in a plane crash in 1986. Machel and Mandela married in 1998, marking Mandela's third marriage and her second. People have carried "get well soon" placards outside the Mediclinic Heart Hospital in Pretoria where Mandela is being treated. They have prayed for him in churches across this nation of roughly 50 million. Schoolchildren have come to his home in Johannesburg to sing. Even though he was not there to hear them, the voices gave solace to his family. "The messages have come by letter, by SMS, by phone, by Twitter, by Facebook, by email, cards, flowers and the human voice, in particular the voices of children in schools or singing outside our home," Machel said in a statement. "We have felt the closeness of the world and the deepest meaning of strength and peace." President Jacob Zuma said Sunday that Mandela remains in serious condition but that his doctors are seeing sustained improvements. Zuma said Mandela is engaging with family during visits. The leader of South Africa's anti-apartheid movement, Mandela spent 27 years in prison during white racist rule. He is vulnerable to respiratory problems since contracting tuberculosis during his long imprisonment. The bulk of that period was spent on Robben Island off the coast of Cape Town where Mandela and other prisoners toiled in a dusty stone quarry. He was freed in 1990 and became South Africa's first black president in 1994. The Nobel Peace Prize laureate divorced his second wife, Winnie, in 1996. However in recent years she has joined him and Machel at family events. Winnie Madikizela-Mandela has been a frequent visitor to Mandela during his latest hospitalization. This marks Mandela's fourth hospital stay since December. Mandela "once said: 'What counts in life is not the mere fact that we have lived. It is what difference we have made in the lives of others,'" Machel said. "I have thought of his words on each occasion the world stood with him, making a difference to him, in his healing."