By Tina Peng and Kate Dailey
Over the past three centuries, the world has seen a flu pandemic every 30 or 40 years. Now, with a massive outbreak spreading across the nation and reaching epidemic levels, medical experts are wondering if this generation’s “big one” has finally arrived.
Before the age of vaccines, millions of people died when new strains cropped up. In 1918 a worldwide outbreak of the Spanish flu killed about 50 million people—more than died in all of World War I. Vaccines were developed in the United States in 1944, but every time the influenza virus mutates into a form against which people have little to no immunity, scientists scramble to create and distribute the new vaccine. Here, a look back at the flu—from the earliest recorded cases to the current crisis.
Here, Luis Puentes, director of emergency preparedness at Lehigh Valley Health Network’s main hospital campus, applies a decal to a mobile tent set up to handle the recent influx of flu cases.

