How Does Seasonal Flu Differ From 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 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 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 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 (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)

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