: The project aims to build the capacity of the Ministry of Health in Haiti to conduct, interpret, disseminate, and respond to assessments, surveys and other evaluations through the implementation of four specific research projects: The first study will focus on the seroprevalence of various specific pediatric infections in Haiti and will be carried out by enrolling 1200 children ages 5-10 and collecting Serum and DBS (dry blood spot) samples to be tested at the National Public Health Laboratory (LNSP) with a focus on vaccine preventable diseases including hepatitis B (ELISA) and IFA for rubella and measles. Analysis will focus on descriptive measures of disease prevalence and patient characteristics associated with various infections. The second study will focus on evaluation of the impact of pneumococcal conjugate vaccine by enrolling approximately 500 children evenly distributed from 0 to 5 years of age and collecting nasopharyngeal specimens to be tested via isolation and conventional serotyping methods at the National Public Health Reference lab in Port-au-Prince. The third study will assess the determinants of HIV mortality through two rounds, retrospective and prospective. The target population will be HIV positive adults of both sexes aged 18 years seen at 15 health institutions from 2005-2009 and the study will compare the survival of ARV-treated versus PLHIV that did not receive treatment. The fourth study will focus on early treatment of PLHIV compared to the standard of care (after CD4 determination. Patients in the test and treat arm will receive treatment within a week of diagnosis concurrent with the pretreatment preparation counseling. The standard of care arm will receive treatment as per current practice (when CD4 <350 and after, pretreatment counseling). All participants will be tested periodically for VL and drug resistance when suppression is not reached (VL > 1000). The primary outcome of the study will be viral load (VL) suppression at 12 months after initiation of therapy. Outcomes will be measured for a period of 5 years.