Chapter 1 1.1 Background The HIV and AIDS pandemic remains one the most serious development crises in the world (WHO, 2006). Women and children bear a disproportionate share of the burden, and in many settings continue to experience high rates of new HIV infections and of HIV-related illness and death. In 2005 alone, an estimated 540 000 children were newly infected with HIV, with about 90% of these infections occurring in sub-Saharan Africa (UNAIDS, 2006) .UNAIDS estimates that approximately