Currently no published data addressing the burden of Human Immunodeficiency Virus (HIV) and Hepatitis B Virus (HBV) co-infection among injecting drug users (IDUs) in Kenya exists. These two viruses share similar routes of transmission, with illicit drug use by injection being the major route of infection. Injecting drug use is a rapidly growing problem in coastal towns of Kenya and the problem is aggravated by sex tourism.This study aimed at determining the prevalence of HBV in HIV positive IDUs and correlating the findings with socio-demographic factors of the study population.A cross-sectional study was conducted using structured questionnaires and laboratory testing of blood samples. Surface antigens for HBV (HBsAg) and anti-HIV antibodies were screened using rapid kits followed by Enzyme Linked Immunosorbent assay tests on positive samples using Hepanostika and Vironostika test kits, for HIV and HBV, respectively. The CD4+ T-cell count was determined by flow cytometry.The prevalence of HIV/HBV co-infection was 14.3% (13/91) with a mean age of 33.2 (SD ± 8.1) years. The mean CD4+ cell count in the HIV/HBV co-infected individuals was significantly lower than HIV mono-infection. Needle sharing and duration of active injection of drugs were significantly associated with HIV/HBV co-infections.This study concludes a potentially high prevalence of HBV/ HIV co-infection in injecting drug users in Malindi, Kenya. With limited evidence on IDU prevalence and its consequences in sub-Saharan Africa, the results of this study highlight the need for a more refined policy on HIV treatment strategy among IDUs. There is a further need for triple testing for HIV, HBV and HCV among suspected IDUs and other associated risk groups like the commercial sex workers before commencement of treatment. Keywords: Injecting drug users, HIV-1, HBV, viral co-infection, Malindi, Keny
