Past Flu Pandemics

An influenza pandemic is a global outbreak of a new influenza A virus that is very different from current and recently circulating human seasonal influenza A viruses. Influenza A viruses are constantly changing, making it possible on very rare occasions for non-human influenza viruses to change in such a way that they can infect people easily and spread efficiently from person to person. Read more about pandemics in recent history.
More Information on Past Pandemics
More information on past pandemics is available from the CDC Archive website.