About Pandemic Influenza

A pandemic is a global infectious disease outbreak. An influenza pandemic occurs when a new influenza A virus emerges for which there is little or no immunity in the human population, begins to cause serious illness and then spreads easily person-to-person worldwide. 

There were three pandemic influenza outbreaks in the 20th century:

• The 1918 pandemic caused at least 675,000 U.S. deaths and up to 50 million deaths worldwide. 
• The 1957 pandemic caused at least 70,000 U.S. deaths and 1-2 million deaths worldwide. 
• The 1968 pandemic caused about 34,000 U.S. deaths and 700,000 deaths worldwide

Flu Terminology

• Seasonal (or common) flu is a respiratory illness that can be transmitted person to person. Most people have some immunity, and a vaccine is available.
• Avian (bird) flu is caused by influenza viruses that occur naturally among wild birds. The H5N1 variant is deadly to domestic fowl and can be transmitted from birds to humans.
• Swine (H1N1) flu is caused by influenza viruses that occur naturally among pigs.  This virus has been transmitted from pigs to humans.

The common symptoms of influenza include:

• Fever - usually over 100.5
• Sore throat
• Cough
• Runny or stuffy nose
• Body and muscle aches
• Fatigue and weakness
• Diarrhea and vomiting (more common among children than adults)

Visit Flu.gov for more information about pandemic influenza.