Bloodstream infection (BSI) is associated with major morbidity and mortality. Population-based studies are the optimal designs to determine the occurrence of BSI. This is because in these designs all cases of BSI occurring in residents of a defined population are included, and where the population at risk is known incidence rates may be determined. Furthermore, selection bias is minimized by inclusion of all cases fulfilling the case definition. Despite the methodological advantages, there is only a small body of published literature investigating BSI at the population level. Few studies conducted since the 1970s have included all aetiologies of BSI and have reported rates between 80 and 189 per 100 000 per year with higher rates reported in more recent years. The three most common aetiologies of BSI are Escherichia coli, Staphylococcus aureus and Streptococcus pneumoniae, which occur at approximate rates of 35, 25 and 10 per 100 000 population, respectively. The incidence of BSI has been demonstrated to vary significantly among regions, and this is in part related to blood culturing rates, population demographic differences and risk factor distribution in regions. Knowledge of the incidence of BSI is important for setting healthcare and research priorities and for evaluating the effectiveness of preventative interventions.
