| Seasonal flu |
Pandemic flu |
| Outbreaks follow predictable seasonal patterns; occurs annually, usually in winter, in temperate climates. |
Occurs rarely (three times in 20th century—last in 1968). |
| Usually some immunity built up from previous exposure. |
No previous exposure; little or no preexisting 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 children and adults, along with other seasonal high risk groups, 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 circulating flu strains and available for annual flu season. |
Vaccine probably would not be available in the early stages of a pandemic. |
| Adequate supplies of antivirals usually available. |
Effective antivirals may be in limited supply. |
| Average U.S. deaths approximately 36,000/year. |
Number of deaths could be quite high (e.g., U.S. 1918 death toll approximately 675,000). |
| 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 (e.g., some school closing, encouragement of people who are sick to stay home) |
Severe pandemic may cause major impact on society (e.g., widespread restrictions 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. |
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