Hospital acquired infections (HAIs) are a major threat to patient safety. This paper addresses the following question: given what is known about the causes of and possible interventions on HAIs, to whom or what should the moral responsibility for preventing these infections be attributed? First, we show how generating robust evidence on the effectiveness of preventive hygiene measures is a complex endeavour and review the existing evidence on the causes of HAIs. Second, we demonstrate that the existing literature on the (...) ethical aspects of infection control has focused on responsibility at the individual-level. Thirdly, we argue that these accounts do not accommodate systemic factors relevant for HAI prevention. We show that the notion of collective responsibility is useful for making understandable how systemic factors, such as employment conditions in hospitals, are both causally and ethically relevant in infection control. (shrink)