The H7N9 subtype of avian influenza virus is one of the influenza A. H7N9 avian influenza is the first new subtype of influenza virus discovered in the world and has not yet been included in our statutory reporting system for infectious disease surveillance and reporting, and there is no vaccine available yet. It is an acute respiratory infection caused by the H7N9 subtype of avian influenza virus. Patients generally present with flu-like symptoms, such as fever, cough, little sputum, and may be accompanied by headache, muscle pain and general malaise. In severe cases, the disease progresses rapidly, manifesting as severe pneumonia, with body temperature mostly persisting above 39°C and respiratory distress, which may be accompanied by coughing up bloody sputum. Rapid progression can occur with acute respiratory distress syndrome, shock, multi-organ failure, and even death. Current knowledge of the clinical features of human H7N9 avian influenza infection is limited, and the viral infection spectrum is unclear; as more information on cases accumulates, the understanding of the disease will change. The subtypes of avian influenza viruses that can infect humans are H5N1, H9N2, H7N7, H7N2, and H7N3. H7N9 avian influenza viruses are novel reassortant viruses with internal genes derived from H9N2 avian influenza viruses, and the incubation period is generally less than 7 days. According to previous information, human avian influenza is disseminated. There is no definite evidence that this H7N9 virus can be transmitted from person to person. Therefore, it is currently not highly transmissible in the population. However, the death rate of human infection with HPAI in the past was very high, about 60%. This time, the H7N9 avian influenza virus, too, has a high morbidity and mortality rate. As of April 8, 2013, 22 cases of human H7N9 avian influenza infection were confirmed, including 7 deaths.