Stay home. Wash your hands. Wear a mask.

Sound familiar? People didn’t give these instructions only in 2020. They also repeated them again and again way back in 1918.

Nobody knows for sure where the Spanish Flu started. (It probably wasn’t Spain. In Spain, people called the sickness the French Flu!) But we know where it spread: everywhere. About one in every three people got the sickness worldwide.

Like COVID-19, influenza affects the respiratory system. Spanish Flu also traveled easily from person to person. Unlike COVID-19, the Spanish Flu commonly put little kids and younger adults in danger as well as older people. What made the influenza strain so bad in 1918? Scientists studying the virus in the last few decades say that particular influenza germ could infect many different types of cells—not just lung cells.

Maybe you or someone you know has been swabbed for COVID-19. But no one could go out and get a Spanish Flu test. Why? People hadn’t even discovered that a virus caused influenza. They knew about microbes. But not enough. Now we have powerful microscopes. They show us exactly which viruses cause each illness. Microscopes hadn’t advanced that much yet in 1918.

The Spanish Flu killed twice as many people as died in World War I. Vaccines had been invented. But there was no vaccine for Spanish Flu. So people did what they could. Even healthy people limited how much they gathered in groups. Sick people stayed isolated (alone) as much as possible.

Have you ever learned about the Spanish Flu in history class? Many have not. In fact, many people—including teachers—just didn’t think about this pandemic much at all until 2020. But now pictures from that unusual year in world history look strangely familiar. People are dressed in old-fashioned clothes. But they also wear masks. Barbers, office workers, policemen—all have their noses and mouths covered to help prevent spreading the Spanish Flu.