Aberrant coagulation causes a hyper-inflammatory response in severe influenza pneumonia

Influenza A virus (IAV) infects the respiratory tract in humans and causes significant morbidity and mortality worldwide each year. Aggressive inflammation, known as a cytokine storm, is thought to cause most of the damage in the lungs during IAV infection. Dysfunctional coagulation is a common complication in pathogenic influenza, manifested by lung endothelial activation, vascular leak, disseminated intravascular coagulation and pulmonary microembolism. Importantly, emerging evidence shows that an uncontrolled coagulation system, including both the cellular (endothelial cells and platelets) and protein (coagulation factors, anticoagulants and fibrinolysis proteases) components, contributes to the pathogenesis of influenza by augmenting viral replication and immune pathogenesis. In this review, we focus on the underlying mechanisms of the dysfunctional coagulatory response in the pathogenesis of IAV.