"Familiarity breeds complacency—“oh, it’s just the flu”—but seasonal influenza is a serious public health problem, causing widespread illness, hospitalizations, and death. The Council of Economic Advisers recently estimated that in a typical flu season, 27 million Americans will get sick; 59,000 will die, while another 368,000 will be hospitalized. The total cost will be $361 billion per year, primarily due to the value of lives lost.
On occasion, new influenza viruses emerge containing significant genetic changes to which people have little or no immunologic memory or protection. These viruses can spread from person to person in an efficient and sustained way, leading to a pandemic with higher rates of illness, serious complications, and mortality than seasonal influenza. The past 100 years have seen four influenza pandemics—1918, 1957, 1968, and 2009—leading to worldwide deaths totaling, respectively, 50 million, more than 1 million, 1 million, and 151,700–575,000. The CEA estimates that a future influenza pandemic would cause $413 billion to $3.79 trillion worth of economic damage in the U.S., depending on the transmission efficiency and virulence of the pandemic virus. U.S. fatalities in the most serious scenario would exceed half a million."