Global concerns regarding novel influenza A (H7N9) virus infections

Severe disease in humans caused by a novel influenza A virus that is distinct from circulating human influenza A viruses is a seminal event. It might herald sporadic human infections from an animal source — e.g., highly pathogenic avian influenza (HPAI) A (H5N1) virus; or it might signal the start of an influenza pandemic — e.g., influenza A(H1N1)pdm09 virus. Therefore, the discovery of novel influenza A (H7N9) virus infections in three critically ill patients reported in the Journal by Gao and colleagues is of major public health significance. Chinese scientists are to be congratulated for the apparent speed with which the H7N9 virus was identified, and whole viral genome sequences were made publicly available in relatively short order. Because this H7N9 virus has not been detected in humans or animals previously, the situation raises many urgent questions and global public health concerns. The key question for pandemic risk assessment is whether...