Flu Virus 101 | National Geographic

Flu Virus 101 | National Geographic

– [Narrator] The flu is a highly contagious respiratory illness. It turns up year after year with devastating consequences. All caused by a most elusive virus. The influenza, or flu virus, is a recurring nightmare. It causes more than 36,000 deaths in the U.S. each year. And was responsible for some of history’s deadliest pandemics.…