Pandemic influenza has occurred on average about once every 30 to 40 years since the 16th century, with the last one occurring almost 40 years ago.
In the last century, there were three influenza pandemics:
- The Spanish Flu in 1918-1919 that killed an estimated 30,000 to 50,000 people in Canada and 20 to 40 million people worldwide.
- Asian Flu in 1957-1958 resulted in about 1 million deaths worldwide.
- Hong Kong Flu in 1968-1969 killed less than 1 million people worldwide.
Experts agree that the world is overdue for another pandemic to appear; however, it is impossible to predict when it will actually arrive.