Clinical symptoms of adult influenza can be clinically categorized into several types: simple type, pneumonia type and toxicity type, which can present with headache, fatigue and other manifestations. 1. Simple type influenza: patients start to get sick very quickly, and may rapidly show systemic toxic symptoms, such as high fever, headache, fatigue, muscle pain, etc. A few cases may have cough, sore throat, hoarseness and other symptoms. A few cases may present symptoms such as cough, sore throat and hoarseness. This type is the most common and has a good prognosis. 2. Pneumonia type: patients may present with persistent high fever, shortness of breath, cyanosis, hemoptysis, extreme fatigue, and even respiratory failure. This type is rare and mainly occurs in infants and young children, the elderly, pregnant women, patients with chronic cardiopulmonary diseases and immunocompromised people. 3. Poisoning type: manifested as systemic toxemia, high fever or obvious damage to the nervous system and cardiovascular system, with high mortality rate and poor prognosis, which is extremely rare. 4. Gastrointestinal type: the main symptoms are vomiting, abdominal pain, diarrhea, loss of appetite, mostly seen in children. When the above symptoms occur, it is recommended to consult a doctor in time to identify the cause and carry out targeted treatment or therapy with the help of a doctor.