Seasonal Influenza |
Pandemic Influenza |
Outbreaks follow predictable seasonal patterns; occurs annually, usually in winter, in temperate climates.
Usually some immunity built up from previous exposure. |
Occurs rarely (three times in the 20th century - last in 1968).
No previous exposure; little or no pre-existing immunity. |
| Healthy adults usually not at risk for serious complications (the very young, the elderly and those with certain underlying health conditions at increased risk for serious complications). |
Healthy people may be at increased risk for serious complications. |
| Health systems can usually meet public and patient needs. |
Health systems may be overwhelmed. |
| Vaccine developed based on known virus strains and available for annual flu season. |
Vaccine probably would not be available in the early stages of the pandemic. |
| Adequate supplies of antivirals are usually available. |
Effective antivirals may be in limited supply. |
| Average U.S. deaths approximately 36,000/yr. |
Number of deaths could be quite high (eg. U.S. 1918 death toll approximately 500,000). |
| Symptoms : fever, cough, runny nose, muscle pain. Deaths often caused by complications, such as pneumonia. |
Symptoms may be more severe and complications more frequent. |
| Generally causes modest impact on society (eg. some school closings, encouragement of people who are sick to stay home). |
May cause major impact on society (eg. widespread restriction on travel, closings of schools and businesses, cancellation of large public gatherings.) |
| Manageable impact on domestic and world economy. |
Potential for severe impact on domestic and world economy. |
