The main manifestations of severe influenza are as follows: 1) fever lasting >3 days and temperature above 39℃; 2) increased respiratory rate, respiratory distress or airway obstruction; 3) change in mental status, drowsiness, convulsions or vomiting. Some children may even become dehydrated in severe cases; 4. The combination of severe pneumonia or necrotizing encephalopathy, or myocarditis, as well as the rapid aggravation of the original underlying disease. In such cases, it is necessary to go to the hospital as soon as possible. Some patients with more serious coughs may even cough up pus or blood sputum, or the child may complain of chest pain or chest tightness.