Discuss as:

Mandela's wife to world: 'Our gratitude is difficult to express'

AP, file

Graca Machel, wife of former president Nelson Mandela, pictured last week, issued a statement thanking people in South Africa and the world for their messages of support for her husband.

Nelson Mandela’s wife Graca Machel thanked the world Monday for messages of support for her husband as he continued to be treated for a lung infection in hospital.

In a statement, Machel said that “so much love and generosity from South Africans, Africans across the continent, and thousands more from across the world, have come our way to lighten the burden of anxiety; bringing us love, comfort and hope.”

“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,” she said. “We have felt the closeness of the world and the deepest meaning of strength and peace.”

/

View images of civil rights leader Nelson Mandela, who went from anti-apartheid activist to prisoner to South Africa's first black president.

“Our gratitude is difficult to express. But the love and peace we feel give yet more life to the simple ‘Thank you!’” she added.

Machel quoted Mandela, 94, as saying “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.”

She said that she thought of his words “on each occasion the world stood with him, making a difference to him, in his healing.”

South Africa’s President Jacob Zuma said on Sunday that the anti-apartheid icon remained in a serious condition in a hospital in Pretoria but added “we are grateful that he continues to get better.”

He has been in the hospital for a week – the fourth time he has been admitted since December.

Mandela's repeated bouts of illness have reinforced a creeping realization among South Africa's 53 million people that they will one day have to say goodbye to their first black president.

Mandela, popularly known by his clan name “Madiba,” has a history of lung problems dating back to his time at the windswept Robben Island prison camp near Cape Town.

He was released from prison in 1990 after 27 years behind bars and was president from 1994 to 1999.

NBC News's Rohit Kachroo and Reuters contributed to this report.

Related: