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Skip Navigation LinksPennsylvania Department of Health > My Health > Emergency Preparedness > Pandemic > Differences Between Seasonal Flu and a Flu Pandemic


Below is a comparison of seasonal flu and a flu pandemic.

Seasonal Flu Flu Pandemic
Outbreaks occur every year, usually in winter. Occurs only rarely (only four times since 1918).
Caused by influenza viruses that are similar to those already affecting people. Caused by a new influenza virus that people have not been exposed to before.
Healthy adults usually not at risk for serious complications. Healthy adults may be at increased risk for serious complications.
Hospitals and healthcare providers can usually meet public needs. Hospitals and healthcare providers may be overwhelmed and difficult to access.
Vaccine available at beginning of flu season. Vaccine would probably not be available in the early stages of a pandemic.
Causes an average of 36,000 deaths each year in the United States. Number of deaths could be significantly higher. In the 1918 pandemic, approximately 675,000 people died in the United States.
Generally does not have a severe impact on daily life. May have a severe impact on daily life, including widespread restrictions on travel, closings of schools and businesses, and cancellation of public events.