The Gut-Iron-Immune Axis in Severe Anaemia and Bacteraemia

Severe anaemia remains a major public health challenge, disproportionately affecting children and women of reproductive age in sub-Saharan Africa. In high-burden settings, the aetiology of severe anaemia is multifactorial, encompassing nutritional deficiencies, infections, and host genetic factors. Beyond its direct clinical consequences, severe anaemia is also associated with increased susceptibility to invasive bacterial infections, particularly those caused by enteric pathogens such as non-typhoidal Salmonella and Escherichia coli. In this review, we present an integrated framework linking severe anaemia and invasive bacterial infection through three interconnected biological pathways, collectively termed the gut-iron-immune axis: gut microbial dysbiosis and impaired intestinal barrier integrity; disrupted iron homeostasis; and impaired immune function. We examine context-specific modifiers in endemic settings, including iron deficiency, malnutrition, malaria, sickle cell disease, and environmental enteric dysfunction. We also discuss how management of severe anaemia, including blood transfusion and iron supplementation, reshapes the gut microbiome, with direct implications for microbial translocation, invasive bacterial infection, and clinical outcomes. Finally, we identify key knowledge gaps and research priorities to guide safer and more effective prevention and management of severe anaemia in high-burden settings.