If a foreign army invaded the United States and in a few months ravaged the population, killing 22 000 men, women, and children and then leaving, the loss would be overwhelming, and the nation would turn its collective efforts to preventing such a tragedy from occurring again . In fact, this invasion occurs almost every year in the United States, but the foreign invader is a pestilence: a new strain of influenza virus. And we are not shocked by the tragedy, and we do not make every effort to prevent its recurrence. While “emerging” infectious diseases—such as those caused by the Ebola virus in Africa, the hantavirus in the United States, and multidrug-resistant bacteria everywhere—hog the headlines, we need to be reminded that a “reemerging” infectious disease, influenza, takes an even greater toll in lives [2–3]. This awareness should prod us to cope more effectively with the almost annual epidemics of influenza while, at the same time, we begin to plan for the next influenza pandemic.