Pandemic Influenza

What is an influenza pandemic?

• Global outbreak of disease
• Occurs when a new influenza A virus appears or “emerges” in the human population
• Causes serious illness
• Spreads easily from person to person worldwide

What is an influenza pandemic?

• Different from seasonal outbreaks or “epidemics” of influenza
• Pandemic outbreaks are caused by new subtypes, by subtypes that have never circulated among people or by subtypes that have not circulated among people for a long time.

Antigenic shift

• Causes an abrupt or sudden, major change in influenza A viruses
• Caused by new combinations of the HA (hemagglutinin) and/or NA (neuraminidase) proteins on the surface of the virus

Steps to a Pandemic

• The appearance of a new influenza A virus subtype is the first step toward a pandemic
• The new virus subtype also must have the capacity to spread easily from person to person

Influenza Pandemics during the 20th Century

• Caused the highest number of known influenza deaths
• More than 500,000 people died in the United States
• Up to 50 million people may have died worldwide

• Caused about 70,000 deaths in the United States

• Caused about 34,000 deaths in the United States

Stages of a Pandemic

• Phase 3: Human infection(s) with a new subtype, but no human-to-human spread or at most rare instances of spread to a close contact

Preparing for the Next Pandemic

• Estimated that in the United States a “medium–level” pandemic could cause 89,000 to 207,000 deaths
• 314,000 and 734,000 hospitalizations
• 18 to 42 million outpatient visits
• Another 20 to 47 million people being sick
• Between 15% and 35% of the U.S. population could be affected by an influenza pandemic
• Economic impact could range between $71.3 and $166.5 billion

Credits

• Most of the information in the slides of this presentation are directly from information contained in the CDC Fact Sheet: “Information About Influenza Pandemics”
• The scanning electron microscope picture is from the CDC Public Health Image Library (PHIL)

For more information, please contact Roy Teramoto, M.D., M.P.H., Phoenix Area IHS, Office of Health Programs.