History of the Influenza Virus

The surface of the influenza virus includes many identical copies of two different proteins H (hemagglutinin) and N (neuraminidase). H is shown as a spike and N is shown as a bulbed-stalk in the influenza virus figure above. Both H and N are required for infection of animals and people. There are many different H and N classified among the bird influenza viruses and they have been given numbered subtypes.

Different strains of influenza virus, called serotypes, have crossed the species barrier from animals 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, influenza pandemics happened four times, in 1918 (H1N1), 1957 (H2N2), 1968 (H3N2), and 1977 (H1N1), killing millions of people globally. It is likely the 1977 event was a re-emergence of H1N1.

In the spring of 2009 a new influenza virus was identified. Originally called "swine flu" because the virus proteins were similar to those produced by viruses that infect pigs, the new virus has been named "2009 H1N1." For more information check this pandemic 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.

Links to additional sites:

Center for Bio Security The Center for Biosecurity is an independent, nonprofit organization of the University of Pittsburgh Medical Center (UPMC). The Center works to affect policy and practice in ways that lessen the illness, death, and civil disruption that would follow large-scale epidemics, whether they occur naturally or result from the use of a biological weapon.

CIDRAP Center for Infectious Disease Research and Policy. Part of the Academic Health Center at the University of Minnesota, CIDRAP fosters the adoption of science-based best practices in public health and conducts original interdisciplinary research.