1. WHO Center for Health Promotion and Prevention Research, School of Public Health, University of Texas, PO Box 20036, Houston, TX 77225, USA
2. WHO Center for Health Promotion and Prevention Research, School of Public Health, University of Texas and The HIV Prevention Research Group, College of Pharmacy, University of Houston, 1441 Moursund Street, Houston, Texas 77030, USA
3. College of Medicine, University of Calabar, Calabar, Nigeria