Influenza

Influenza, abbreviated as flu, is an acute respiratory infectious disease caused by influenza virus, which is mainly spread along with droplets with strong infectivity. The influenza virus may cause epidemics or pandemics of influenza and its incidence ranks the first among legally listed infectious diseases. The prevalence of influenza peaks in autumns and winters, with short illness course and self limitation. However, influenza can be complicated by pneumonia or other serious complications that may cause death in populations of infants, young children, the elderly, those with underlying heart and lung disease and those with compromised immunity.