The growth and virulence of many pathogens is stimulated by iron, and hepcidin has evolved to downregulate the absorption and circulation of iron when it detects a threat of infection (signalled by inflammatory cytokines, including interleukin-6).7, 8 Among children living in unhygienic environments with recurrent infections and chronic inflammation, hepcidin is frequently upregulated,9 downregulating iron absorption.10 The gene discussed is HAMP; the disease is infection.