South Africa has more people living with HIV, an estimated 6.6 million, than any country in the world. About half are now receiving antiretroviral (ARV) treatment, which has greatly stressed the country's health care system. Now, South Africa plans to encourage all infected people to learn their status and start treatment as part of the drive to end its epidemic. The cornerstone of the campaign is the fact that HIV-infected people who take ARVs and fully suppress their virus rarely transmit to others.