History of Influenza
Different strains of influenza virus, called serotypes, have crossed the species barrier from birds to humans. Clinical and epidemiological records show that ten influenza pandemics have occurred in the last 300 years, with an average of one per 33 years. During the 20th century, highly pathogenic avian influenza (HPAI) pandemics have happened four times, in 1918 (H1N1), 1957 (H2N2), 1968 (H3N2), and 1977 (H1N1), killing millions of people globally. In all four pandemics, HPAI originated from the avian influenza viruses. For more information check this history of influenza informative site. It is a one-stop access to U.S. Government avian and pandemic flu information.
The 1918 influenza pandemic “Spanish flu” was particularly devastating, resulting in the demise of an estimated 20 to 40 million people worldwide. Influenza experts are concerned that the increasing frequency of outbreaks with the current H5N1 virus has the possibility for another influenza pandemic like the 1918 influenza pandemic which can potentially cost the globe over 160 million lives.