Influence is a highly contagious, usually self-limiting, viral upper respiratory illness. The severity of symptoms depends on the type of virus and the underlying medical condition of the infected person. The World Health Organization estimates that approximately 3 to 5 million cases and 250,000 to 500,000 deaths occur annually from influenza. The introduction of influenza vaccination has significantly reduced the number of cases, hospitalizations, and related deaths, especially in vulnerable groups.
Influence
