1. AIDS Virus Research Unit, National Institute for Communicable Diseases, Sandringham 2131, Johannesburg, South Africa
2. Division of Medical Virology, University of Cape Town, Cape Town, 7925 South Africa
3. Innovir Institute, Bedfordview, Johannesburg, 2047 South Africa
4. Private Physician, Johannesburg, 2008 South Africa
5. Department of Virology, University of the Witwatersrand, Johannesburg, 2193 South Africa