Key Differences Between Seasonal and Pandemic Influenza
Occurs every year during the winter months.
Can occur in any season; historically occurs three to four times a century.
Affects 5-20 percent of the U.S. population.
Experts predict an infection rate of 25-50 percent of the population, depending on the severity of the virus
Annually kills between 500,000 and 1 million people worldwide including 36,000-40,000 in the U.S.
The "Spanish Flu" of 1918 killed 500,000 in the U.S. and 50 million worldwide.
Most people recover within one or two weeks.
Usually associated with a higher severity of illness and a higher risk of death.
Deaths generally confined to "at risk" groups:
All age groups may be at risk for infection, not just "at risk" groups: