influenza

Influenza (influenza for short) is a common acute respiratory infection caused by influenza virus. It is more common in winter and spring. It is also a highly contagious and fast-moving disease. It is mainly transmitted through droplets in the air, person-to-person contact, or contact with contaminated items. Clinical features are high fever, fatigue, headache, general soreness and other symptoms of systemic poisoning, while respiratory catarrh is mild. Flu virus is susceptible to mutation and is highly infectious, often causing influenza epidemics. In the 20th century, there were 4 world pandemic influenza A pandemics. In the past half century (1953 to present) in China, there have been 17 large, medium and small-scale influenza epidemics, including 2 pandemics. From 1918 to 1919, a very widespread worldwide pandemic occurred, causing 20 million deaths.