Over the next few weeks, at least, Americans are being asked to stay home. Schools and restaurants are closing down. Public events and larger gatherings are getting canceled, if not banned. People are advised to not even have friends over. All of this amounts to a huge disruption in American life.

But it’s not the first time the US has done this.

Back in 1918, a strain of influenza — colloquially called the “Spanish flu” — caused the worst pandemic in centuries, killing as many as 100 million people. In the US, about 675,000 people died.

In response, states and cities across the country told people to do what we now know as social distancing. Schools, restaurants, and businesses were closed. Public gatherings were banned. People were told to isolate and quarantine. In some places, this lasted for months.

It worked. Things didn’t go perfectly — far from it, as some cities fared much worse than others, and people didn’t always obey what experts and officials were telling them. But studies show that the social distancing efforts helped slow the spread of the 1918 flu and reduce the mortality rate overall.

One of the key lessons: It’s important not to give up too early. Over the past few days, government officials — most prominently, President Donald Trump — have suggested pulling back social distancing efforts. But in city after city during the 1918 flu pandemic, giving up on such measures early consistently caused flu cases and deaths to rise again.

Things are obviously quite different in the US now than they were a century ago. For one, people in 1918 didn’t even know the flu was caused by a virus, nor did they have the ability to quickly develop and deploy new vaccines. Today, we know exactly what the enemy is — the SARS-CoV-2 virus, which causes the disease Covid-19 — and we are already developing vaccines for it (though slower than just about everyone would like).

But that makes it all the more remarkable that social distancing was a success. It shows that these public health strategies, as simple and intrusive as they are, do help save lives. And if we could do it back then, there’s a very good chance we can do it now.

“I think we’ll get through it,” Howard Markel, director of the University of Michigan’s Center for the History of Medicine, told me.

Here’s what we can learn from the social distancing experience of the 1918 flu pandemic, and what we can’t.

1) Early, sustained, layered action saved lives

Perhaps the most important takeaway from the 1918 flu: We need to take action quickly, we need to sustain interventions until the virus truly goes away, and we need to do all we can in the meantime.

The most successful approaches in 1918, Markel found in his 2007 study published in JAMA, followed those three components. First, they were early — particularly before the flu got to an inflection point in which the virus infected a certain amount of people and spread rapidly. Second, they were sustained — lasting until the virus really seemed to go away, and quickly redeployed if the virus came back.

Third, the best approaches were layered. It wasn’t enough to just tell people to stay home, because they might feel the need to go to school or work, or they could just ignore guidance and go to events, bars, church, or other big gatherings anyway. Making it harder to do any of that by placing restriction on top of restriction helped. In practical terms, this meant advising against or prohibiting just about every aspect of public life, from schools to restaurants to entertainment venues (with some exceptions for grocery stores and drugstores).

“Each [policy] is like a slice of Swiss cheese,” Markel said. “You want to layer them over one another so the holes are smaller.”

Another 2007 study, published in PNAS, backed this up: “Consistent with this hypothesis, cities in which multiple interventions were implemented at an early phase of the epidemic had peak death rates ≈50% lower than those that did not and had less-steep epidemic curves. Cities in which multiple interventions were implemented at an early phase of the epidemic also showed a trend toward lower cumulative excess mortality, but the difference was smaller (≈20%) and less statistically significant than that for peak death rates.”

That, essentially, describes “flattening the curve”: spreading out the rate of infection so health care systems don’t get overwhelmed and are, therefore, better equipped to treat patients back to good health.

Unfortunately, we know the early, sustained, and layered strategies worked because not all US cities did them well, allowing comparisons. Consider this chart from the PNAS study, which shows that Philadelphia had a much bigger spike in deaths, while St. Louis kept its death toll down overall:

Philadelphia got less of a warning about the 1918 flu — the chart shows its first cases were ahead of St. Louis’s — and that limited its ability to respond somewhat. But even given that, Markel said, Philadelphia just did a much worse job than St. Louis at putting in place social distancing measures. Philadelphia, as just one example, didn’t cancel a World War I parade as the 1918 flu picked up, which likely led to thousands of infections.

2) Cities that eased restrictions early saw a spike in cases

Another point worth emphasizing from the research: Social distancing practices have to be sustained. As obstructive as it is that we might need to do some social distancing for months, that really might be what’s necessary to save as many lives as possible.

Markel’s study demonstrates this: As the pandemic appeared to subside, St. Louis pulled back its social distancing measures. But it turned out that the pullback was premature — and flu deaths started to rise once again. This graph shows that, with the line chart tracking flu deaths over time and the black and gray bars below showing when key social distancing measures were in place:

In a lot of cities, similar premature pullbacks produced a lot of “double-humped epi curves,” as Markel described them: Officials instituted social distancing measures, saw flu cases fall, then pulled back the measures, saw flu cases rise again, and reactivated the measures.

Notably, the second spike in deaths only appeared when cities removed social distancing measures, Markel’s study found: “Among the 43 cities, we found no example of a city that had a second peak of influenza while the first set of nonpharmaceutical interventions were still in effect.”

The PNAS study, which looked at 17 US cities, reported similar findings: “no city in our analysis experienced a second wave while its main battery of [nonpharmaceutical interventions] was in place. Second waves occurred only after the relaxation of interventions.”

The lesson here is to not take social distancing measures for granted. This will be a hard call to make, because it’s going to be difficult to predict when the coronavirus is truly gone. And the public health gains have to be weighed with the strain that social distancing is and will continue to put on families — especially those who need to leave their homes for their only source of income — and the economy overall.

But the hard lesson is that social distancing may be needed for months, maybe even until a vaccine is produced a year or so from now, to save lives. As the PNAS study concluded: “In practice, and until emergency vaccine production capacity increases, this means that in the event of a severe pandemic, cities will likely need to maintain NPIs for longer than the 2–8 weeks that was the norm in 1918.”

3) Seeing the effects of outbreaks drove people to serious action

The question, given the reality of how long social distancing may be necessary, is how people are going to get through this. Even beyond the damage to the economy and the loss of income involved, people are going to miss out on a lot of the experiences that enriched and validated their lives before. Experts worry social distancing, even if it’s necessary, just won’t be sustainable for weeks or months.

But people did do social distancing for weeks and months during the 1918 flu pandemic.

Markel gave one potential explanation for that: People were already very familiar with the risk if they didn’t social distance. Back then, disease epidemics and pandemics of all kinds were common. Just about everyone knew someone — from parents to aunts and uncles to children — who died of disease.

People “were all used to living through epidemics all the time. There was a flu epidemic in the 1890s. There was a bad polio epidemic in 1916. There were diphtheria, pertussis (whooping cough), measles, chicken pox, and smallpox epidemics during that period,” Markel said. “Contagious diseases and their deadly effects were part of people’s lives. So they understood when the doctor quarantined them what that meant.”

Today, very few of us have these experiences. There hasn’t been a major pandemic that hit the US hard in decades — the most recent example is HIV/AIDS, though that didn’t require social distancing but safer sexual practices.

“We’re almost a victim of our own success,” Markel said. “I’d rather be that way, frankly, because we have vaccines, antibiotics, and all these other things. But very few of us know about it.”

The flip side is that, as people see the result of Covid-19 in their communities, they might be driven to more action. That may help people sustain periods of social distancing that seem unbearable today.

The hope, however, is it doesn’t take that — and people social distance before coronavirus gets so bad that much of the population sees the damage it can cause firsthand.

4) We need serious leadership to help guide us through all of this

One of the key lessons from the comparison between St. Louis and Philadelphia: Good leadership makes a difference.

“In 1918, there were some cities that had really good leaders. They had really good health commissioners who worked well with mayors and worked well with the superintendent of schools and police force and what have you,” Markel said. “And then there were others that were really bad. In Pennsylvania, the mayors of Philadelphia and Pittsburgh were fighting with the governor, and the governor was fighting with the state health commissioner.”

This, experts say, is key: Americans are being asked to make sacrifices — potentially isolating themselves from their loved ones, giving up activities they value, and maybe losing income. It’s on the nation’s leaders to guide Americans through this, assuring them that they’re doing the right thing and that there’s a light at the end of the tunnel.

“You really need very strong leadership from the top,” Céline Gounder, an epidemiologist at New York University, told me.

So far, that level of leadership has been lacking from the White House. Trump has downplayed the coronavirus, at one point suggesting it would miraculously disappear and at another claiming that concerns about it are a “hoax.” He’s contradicted his own public health experts. His administration has been slow to react to the pandemic, whether it’s providing adequate testing or providing clear guidance on what people should do.

Ashish Jha, director of the Harvard Global Health Institute, previously called the Trump administration's messaging “deeply disturbing,” adding that it’s “left the country far less prepared than it needs to be for what is a very substantial challenge ahead.”

Some of this played out in the 1918 flu pandemic, as government officials played down the outbreak to avoid demoralizing the country during World War I. This likely hurt the response to the crisis.

“The lack of trust made it harder to implement critical public health measures in a timely way, because people just didn’t believe what they were being told,” historian John Barry told Vox. “And by the time the government was forced to be transparent about the situation, it was mostly too late. The virus was already widely disseminated. So the lying and the lack of trust cost a lot of lives.”

The good news is some places were still able to take action to mitigate the pandemic. As the crisis became more apparent, different cities, states, and the country as a whole pulled together.

Maybe something similar will play out now, Markel said. “When Americans have been challenged with crises in the past, as a nation we’ve managed to get together to forget about our differences and maximize our similarities in working together.”

5) We’re in a much better place to handle a pandemic than we were 100 years ago

All the lessons of 1918 come with a big, obvious caveat: A lot has changed in the past century. We have much more accessible commercial airplanes. We have the internet. We have smartphones. America is much less rural than it was back then, which surely helped with isolation.

We also have a much better health care system. From the development of vaccines to all sorts of antibiotics to all kinds of other medications, the world is much better equipped to deal with any sort of disease. To this point: Some of the people at greatest risk of Covid-19 are those with chronic conditions like cancer, diabetes, HIV, and so on. “These are people who would never be walking in 1918,” Markel said. “They’d be dead.”

The quality of health care providers has improved, too. “In 1910, there was a famous medical report called the Flexner Report that closed within a year about half the American medical schools,” Markel said. “In 1918, there were still a lot of those graduates working. Some were botanical doctors, and some were homeopaths, and some were eclectic doctors — they all had the degree, MD, but it wasn’t modern medicine.”

People didn’t even know the flu was caused by a virus. Jeremy Brown, author of Influenza: The 100-Year Hunt to Cure the Deadliest Disease in History, described alternative theories:

Some suggested it was a misalignment of the planets. (That’s what gave us the name influenza, from the Italian word for “influence.”) Others believed the cause was tainted Russian oats, or volcanic eruptions. Microbiologists focused on a bacterium they had discovered decades earlier in the lungs of influenza victims, and called it Bacillus influenza. But they had merely recognized a bacterium that invades lungs already weakened from influenza. Not until 1933 did two British scientists demonstrate that the cause must be a new class of disease, which today we call viruses. Finally, in 1940, the newly invented electron microscope took a picture of the influenza virus, and for the first time in history we could not only name, but also see, the culprit.

None of this is to say everything is perfect. Experts warn that we are still unprepared for a major pandemic, like the one we are facing now. Even though we can make vaccines, they can’t be turned around instantly — and potentially thousands if not millions of people could die in the next year as a coronavirus vaccine is developed.

But it’s still a much better place to be than 100 years ago. And we’re discovering new, better treatments for all kinds of diseases all the time.

“There’s never been a better time in human history to have a pandemic than today, with the exception of next week or a month later,” Markel said. “You want to kick that can down the road, but it’s here.”