Questions & Answers
Influenza - Pandemic - The Disease
Back to Parent Q&A Category Back to All Influenza - Pandemic Q&A Back to All Q&A Back to Influenza - Pandemic

Seasonal Influenza vs. Pandemic Influenza

  1. How is seasonal influenza different than pandemic influenza?

    Key Differences Between Seasonal and Pandemic Influenza

    Seasonal Influenza

    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:

    • Elderly (over 65 years of age).
    • Young children aged 6-23 months.
    • Persons with existing medical conditions (i.e., lung disease, diabetes, cancer, kidney, or heart problems, or compromised immune systems).

    All age groups may be at risk for infection, not just "at risk" groups:

    • Otherwise fit adults could be at relatively greater risk, based on patterns of previous epidemics.
    • For example, adults under age 35 (a key segment of the U.S. workforce) were disproportionately affected during the 1918 pandemic.

  2. What are the symptoms of pandemic influenza?
    Symptoms of pandemic influenza are the same as seasonal influenza:  i.e., fever, cough, sore throat, body aches, headaches, chills, fatigue and sometimes diarrhea and vomiting.  Although the symptoms are similar, the onset of illness can be rapid and aggressive, causing an increased need for early hospitalization and treatment, especially in high-risk groups susceptible to complications associated with the influenza virus.