Johnson was born Xolani Nkosi to South African parents infected with HIV, and he was born infected. When he was two he was taken from his mother who by now was too ill to care for him, and she has since died.
He was placed with Gail Johnson, a white woman, who cares for 20 children with HIV and 11 of their mothers. Whether he was formally adopted or not is unclear from his obituaries, which use the terms interchangeably.
In 1997 his mother challenged his exclusion from school because of his AIDS and won, and he attended school normally until not long before he entered the final stages of AIDS in December 2000. He died in his sleep in June 2001, aged just 12 years.
In the few years before he died Nkosi became a South African and international icon and symbol of the struggle against AIDS, especially challenging his own government's abysmal record in providing medical and social help for HIV-affected people and their families. His last speaking engagements included the 13th International AIDS Conference in Durban, South Africa in July 2000 and another AIDS conference in August in Atlanta, Georgia.