Transmission of hepatitis B, hepatitis C and human immunodeficiency viruses through unsafe injections in the developing world: model-based regional estimates

Thousands of millions of injections are delivered every year in developing countries, many of them unsafe, and the transmission of certain bloodborne pathogens via this route is thought to be a major public health problem. In this article we report global and regional estimates of the number of hepa titis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency vir us (HIV) infections that may occur from unsafe injections in the developing world. The estimates were determined using quantitative data on unsafe inj ection practices, transmission efficiency and disease burden of HBV, HCV an d HIV and the prevalence of injection use obtained from a review of the lit erature. A simple mass-action model was used consisting of a generalized linear equa tion with variables accounting for the prevalence of a pathogen in a popula tion, susceptibility of a population, transmission efficiency of the pathog en, proportion of injections that are unsafe, and the number of injections received. The model was applied to world census data to generate conservati ve estimates of incidence of transmission of bloodborne pathogens that may be attributable to unsafe injections. The model suggests that approximately 8-16 million HBV, 2.3-4.7 million HCV and 80 000-160 000 HIV infections ma y result every year from unsafe injections. The estimated range for HBV inf ections is in accordance with several epidemiological studies that attribut ed at least 20% of all new HBV infections to unsafe injections in developin g countries. Our results suggest that unsafe injections may lead to a high number of infections with bloodborne pathogens. A major initiative is there fore needed to improve injection safety and decrease injection overuse in m any countries.