Influenza (hereinafter referred to as influenza) is one of the major public health problems facing humanity. The most notable epidemiological features of influenza are: sudden outbreaks, rapid spread, resulting in epidemics of varying degrees of severity, seasonality, and high morbidity but low morbidity and mortality (except for human infection with highly pathogenic avian influenza). Seasonal influenza can generally cause acute respiratory illness with fever, with a rapid onset, and although mostly self-limiting, hospitalization is required for severe infections or complications; the high-risk groups for severe cases are mainly the elderly, young children, pregnant women, or those with chronic underlying illnesses; and a small number of severe cases can die from respiratory or multiple organ failure. Human infection with highly pathogenic avian influenza (hereinafter referred to as human avian influenza) disease and death rate of up to 60% or more. Vaccination is the main method of prevention and control of influenza. Early treatment with anti-influenza viral drugs can alleviate influenza symptoms, shorten the duration of illness, reduce the incidence of complications, shorten the time to detoxification, and possibly reduce the case fatality rate; during epidemics, prophylactic use may reduce the prevalence rate. After the global influenza A (H1N1) epidemic in 2009, in order to further strengthen the clinical prevention and treatment of influenza and to make corresponding preparations, China still urgently needs a diagnosis and treatment guideline reflecting the latest progress of influenza and guiding the actual clinical work. Therefore, the Ministry of Health organized experts in the field of influenza prevention and treatment research in China in the areas of pathogenesis, epidemiology, laboratory diagnosis, clinical practice, traditional Chinese medicine, disease prevention and control, etc. On the basis of summarizing China’s previous influenza diagnostic and treatment protocols and clinical experience, and with reference to the latest research results from both home and abroad, it formulated the “Guidelines for Diagnosis and Treatment of Influenza (2011 Edition)” suitable for China’s clinical use. The Guidelines mainly cover the latest comprehensive information on influenza pathogenesis and epidemiology, clinical manifestations, diagnosis and differential diagnosis, treatment and prevention, etc., in order to guide the improvement of China’s influenza diagnosis and prevention, and to mitigate the hazards of influenza on human health and society.