Common influenza is an acute respiratory infectious disease caused by influenza virus, which is mainly transmitted through air droplets. Clinically, there are acute onset of high fever, fatigue, generalized muscle pain, conjunctivitis obvious and mild respiratory tract infection symptoms, although self-limiting, but the elderly and people with chronic respiratory disease, heart disease is easy to complicate pneumonia. The most important characteristic of influenza is epidemic, which can cause regional pandemic. Generally, there is a peak of pandemic in 3 years. Avian influenza, early symptoms are very similar to severe influenza, manifested as high fever, runny nose, nasal congestion, cough, sore throat, headache, general malaise, some patients may have nausea, abdominal pain, diarrhea, dilute watery stools and other gastrointestinal symptoms. Eye infections such as conjunctivitis can be seen in some patients, and the body temperature mostly stays above 39°C. Chest X-ray may show unilateral or bilateral pneumonia in some patients, with pleural effusion in a few. Some patients may develop acute respiratory distress syndrome and other serious life-threatening syndromes. Patients with avian influenza often have a history of avian exposure, whereas most people who do not have recent avian exposure are generally not considered to have avian influenza.