Th2-type inflammation under conditions of pre-existing chronic disease is associated with liver damage in patients with avian influenza H7N9 virus.

Most patients infected with avian H7N9 influenza virus develop severe disease, including respiratory failure, acute respiratory distress syndrome (ARDS), and multi-organ failure. The pathogenesis of H7N9 infection is not fully understood. This study revealed that H7N9-infected patients who had fatal outcomes or critical illness all had pre-existing chronic diseases. The patients did not have obvious systemic inflammation compared to the healthy controls. However, their fatal outcomes and critically severe illness were significantly associated with high serum levels of tumor necrosis factor (TNF)-α. Interestingly, the degree of liver damage in these patients significantly correlated with their serum levels of Th2 cytokines, interleukin (IL)-4, and IL-9. Taken together, our results suggest that Th2-type inflammation in H7N9-infected patients with pre-existing chronic diseases likely contributes to the pathogenesis of H7N9 infection and is linked to poor clinical outcomes.