A million text messages a day will be sent as part of a new scheme to encourage South Africans to be tested for HIV.
Project Masiluleke has been described as the largest use of mobile phone technology for health promotion.
Texts include: “Worried that you might have HIV and want to talk to a counsellor about getting tested? Call Aids helpline 0800012322.”
During a pilot project earlier this year calls to the National AIDS helpline rose from 1,000 to 4,000 a day.
Six million South Africans are HIV positive, according to UN figures, and every year 350,000 die from AIDS-related illnesses.
“South Africa is the epicentre of the global HIV epidemic,” Zinny Thabethe, an HIV activist, told the BBC.
“You would think that in a country where it is so obvious that we are challenged by HIV that there would be enough knowledge to help people access care or change behaviour.
“HIV testing is widely available, but only 5% have managed to test for HIV.
“Most people only get a test when they are about to die.”
Mobile phones have near universal coverage in South Africa.
“As South Africans we have to take a stand and we have to take responsibility to solve our crisis,” said Ms Thabethe.