Former South African President Nelson Mandela continues to recover in hospital from a lung infection but remains in a serious condition, South African President Jacob Zuma said on Sunday. Mandela has been in a Pretoria hospital for a week, the fourth time the 94-year-old former president and anti-Apartheid leader has been admitted to hospital since December. "We are grateful that he continues to get better," Zuma said. "Over the last two days, although he remains serious, his doctors have stated that his improvement has been sustained." Zuma was addressing a gathering for Youth Day in eMadadeni in the KwaZulu-Natal province in remembrance of the 1976 Soweto youth uprisings against apartheid, Reuters reported.