That phrase and charts illustrating the concept were everywhere in mid-March, shortly before the New York City outbreak exploded. The city would see 10,000 cases and nearly 1,000 deaths every day by early April.
Covid-19 cases were spiking, and hospital systems risked being overwhelmed by patients with life-threatening symptoms. If hospitals ran out of beds or ICU units, nurses, or doctors, people would die unnecessarily — from Covid-19 and other causes. The way to prevent such a tragedy was to lock down. Flattening the epidemiological curve would keep the caseload manageable for our health system.
“If you look at the curves of outbreaks, they go big peaks, and then come down,” Anthony Fauci, the nation’s top infectious disease expert, said on March 10. “What we need to do is flatten that down.”
Vox wrote an explainer on the idea. Barack Obama shared it with his tens of millions of Twitter followers. “Flatten the curve” became a public health meme — there was even a Fauci bobblehead that incorporated it — but it was also an urgent call to action.
The US did succeed at flattening the curve — at least at first. Businesses closed and most states issued stay-at-home orders; later research concluded those lockdown measures helped prevent tens of millions of Covid-19 cases.
But America failed to take advantage of that window to ramp up its virus testing and tracing capabilities, and states quickly faced intense pressure to relax their policies to alleviate the economic costs of the shutdowns. Reopening began earlier than public health experts believed it should. The political will to impose new lockdowns had evaporated by the time cases spiked again.
At the end of 2020, with more than 20 million Covid-19 cases and nearly 350,000 deaths in the US, it is evident that trying to flatten the curve was not sufficient to end the pandemic. That doesn’t mean it failed entirely. Slowing the spread of Covid-19 was meant to buy time to figure out what came next. But the US never did.
America’s political leaders did not establish clear, shared goals for managing the outbreak. And eventually the Covid-19 response became politicized, driving Americans apart on the value of wearing masks or social distancing rather than maintaining the solidarity necessary to stamp out a highly infectious virus.
Flattening the curve became an abstraction with no real meaning.
“The value of ‘flatten that curve’ was in the context of that first surge,” Albert Ko, who leads the epidemiology department at the Yale School of Public Health, told me, “and then it lost its value.”
Flattening the curve worked — at first
Flattening the curve was already a well-understood concept in public health circles. But the Covid-19 pandemic presented the first real opportunity to put it to the test.
“Initially, it really hit home for people when they saw the images of overcrowded hospitals,” Leana Wen, the former Baltimore city health commissioner, told me. “The ‘flattening the curve’ concept made sense when people realized it was about making sure hospitals didn’t get too crowded.”
“There are many millions of Americans who made profound sacrifices, and continue to do it to this day,” she continued. “But it was inconsistently applied.”
It may be difficult to remember now, but back in March, Americans were mostly unified in embracing the strategies necessary to flatten the curve. The vast majority of states closed businesses and schools. Polling showed that people were willing to take social distancing measures.
New York faced plenty of challenges (the virus was likely spreading for weeks in the NYC area before it was detected) and made its share of mistakes (sending infected patients back to nursing homes). But the proof of the strategy’s success was in the curves. Until the recent winter surge, they were flat.
Multiple studies have found that mitigation measures suppressed the virus’s spread and likely prevented millions of cases — and with them many deaths. A study published in Health Affairs in May found that social distancing policies, particularly stay-at-home orders and closing bars and restaurants, had staved off as many as 35 million cases in the US by the end of April. More recent research published in Science concluded that closing schools and businesses, as well as limiting the size of private gatherings, reduced spread considerably.
“NYC flattened the curve. Other places delayed it,” William Hanage, an epidemiologist at Harvard University, told me. “But that ought to provide an opportunity to ramp up testing and health care and prepare people for the long haul. You know that did not happen.”
Experts came up with roadmaps for how to proceed once the initial curve was flattened. A proposal from the American Enterprise Institute set specific thresholds for case numbers, hospital capacity, and testing that were designed to allow states to safely begin relaxing their lockdown measures once the virus had been sufficiently suppressed and the health system’s capacity had been expanded.
But the Trump administration never embraced those plans. Instead, the president often said that the cure (lockdowns) could not be worse than the disease (Covid-19). The White House eventually settled on a message that the US would need to learn to live with the virus.
America’s failures to establish an effective test-trace-isolate program are well documented. Some experts question whether contact tracing could have been as effective in a country like the US as it has been in somewhere like South Korea, which is much smaller and has laws that allow government authorities to intrude on personal privacy in the name of public health. But everybody I spoke to agreed the United States had not made the best use of the time afforded by flattening the initial Covid-19 curve.
Instead, many US states that had avoided the worst of Covid-19 in the spring saw the lack of an outbreak as a sign that they could push ahead with reopening. Once the curve was flat, the political will to keep it that way began to crumble.
America wasn’t the only place to struggle with figuring out how to move forward from its spring lockdown; many European countries saw their own second waves over the summer. But the missed opportunity still set the course for the rest of the pandemic.
“We never really came up with a plan to transition,” Caitlin Rivers, a senior scholar at the Johns Hopkins Center for Health Security who co-authored the AEI roadmap back in March, told me.
The Covid-19 pandemic revealed the limits of “flatten the curve”
In some ways, flattening the curve did work as intended.
Hospitals have not — yet — been overwhelmed, as they were in the dire situation in Lombardo, Italy, in the spring. But today, with cases and hospitalizations still rising, US hospitals warn they are again nearing a breaking point.
Slowing the spread of the disease in the spring also gave scientists a chance to learn more and more about the virus.
Among other things, they learned that people were the most infectious before they showed symptoms. They figured out the virus primarily spread through respiratory droplets, not through touch or surfaces. The elevated fatality risk to the elderly became more apparent. Researchers quickly began to figure out which treatments worked (putting patients in a prone position, administering remdesivir and dexamethasone) and which ones didn’t (the Trump-favored hydroxychloroquine).
With this information, the US could have used the time it bought by flattening the curve to figure out whether more targeted interventions would work better than lockdowns, as the Science study suggested, and whether individual cities or counties could best manage their own outbreaks.
“Do we need strong interventions rather than calibrated? Do you have to have regional interventions in order to really make a dent?” Ko said. “I think we’ve been in that kind of limbo. Europe couldn’t calibrate that. They had to go into lockdown.”
The cost of that failure has not been paid equally. The pandemic underscored the many inequities in American life, starting with who contracts the virus and who dies from it. Black and Hispanic Americans have been disproportionately affected by Covid-19, both in terms of health and the toll of the year’s economic downturn.
When the curve didn’t stay flattened, the people who had to go into work, who live in intergenerational households, and who have higher rates of chronic disease were the most at risk.
“I don’t think we ever fully appreciated how the messaging around flattening the curve, how the challenges we as a nation face, would affect the most vulnerable,” Utibe Essien, a professor of medicine at the University of Pittsburgh, said. “The people who didn’t have the same access to staying at home, masking up, who didn’t have the same opportunities to do jobs that didn’t increase their exposure.”
And in other ways, flattening the curve still failed to accomplish its goal of preserving health care access. While hospitals have not yet been completely overwhelmed, some people aren’t getting the care they need. ProPublica reported that over the summer in Houston, medical examiners saw a spike in the number of people found dead in their homes. Some of those deaths were from Covid-19; some were from heart attacks, strokes, and other conditions. Either way, the news of the virus’s rapid spread in the area may have kept people from seeking medical assistance, with deadly consequences.
Throughout the year, with cases staying stubbornly high, doctors warned about the consequences of non-Covid-19 patients postponing care for chronic or emergent conditions. Research showed that visits to primary care doctors and specialists dropped precipitously in the spring and summer.
Health care experts fear that patients who may have been experiencing an onset of conditions like diabetes or heart disease will face setbacks if they delayed seeing a doctor to get an initial diagnosis. It will take years to fully understand those long-term effects.
“It’s like a lost year of care,” Essien, a practicing physician, told me.
The US never pivoted from flattening the curve
Now, with 2020 coming to an end and the US reporting, on average, 180,000 new cases and more than 2,000 new deaths every day, there is no more hope for flattening the curve.
Luckily, vaccine development has been speedy and people are already being vaccinated against the coronavirus. But public health leaders still expect tens of thousands more deaths in the months before the country can achieve widespread protection among the population.
As a public health message, despite the initial success, “flatten the curve” has lost its force and America’s public health leadership failed to adapt and find a new message that would resonate with people.
David Rehkopf, a social epidemiologist at Stanford University, drew a comparison to the anti-smoking campaign. Putting a surgeon general’s warning on cigarette boxes did have a quick and dramatic effect on smoking rates, but not everybody stopped smoking. Public health leaders had to pivot to new strategies to keep making progress.
“With Covid-19, all of this was compacted into less than a year, not decades,” he said. “Adapting that quickly is tough, but from past public health campaigns, we should have anticipated the need to do this.”
When I reported on Melbourne, Australia’s success in eradicating Covid-19, I learned that the policy experts there worried that slogans like “flatten the curve” or “slow the spread” were too vague. The public health authorities there instead came up with a detailed step-by-step guide for how they would, eventually, get Covid-19 cases down to zero.
Specific thresholds were set: Once we reach X number of cases per day, then we can reopen Y. That strategy, despite some controversy, has been a success.
But in the US, many states, under pressure from businesses losing weeks of revenue and from anxious constituents who saw no immediate emergency in their daily lives, began to quickly lift their social distancing policies in the spring, once the curve seemed to flatten. Texas, which put a fairly toothless stay-at-home order into place at the start of April, lifted it a month later. By the end of June, its number of daily cases had increased 600 percent.
There was no unified voice communicating to the public what mitigation measures were necessary, why, and what outcome we were working toward. (New York Gov. Andrew Cuomo, who held daily briefings in the spring with handy slide presentations to convey the current state of the outbreak and what would be coming next, was largely an exception among his peers.) The CDC was sidelined by the Trump administration throughout the year.
Instead, 330 million Americans were left to make their own risk assessments — or not.
Given the research that shows a small percentage of infected people account for a very large share of the transmission, that was a recipe for disaster. And rather than take proactive measures as infection rates first ticked up, which public health experts say are most important given the pre-symptomatic spread of Covid-19 and its slow gestation, governors seemed to be paralyzed and waited to act until the crisis was already upon them.
“Every American’s personal definition of Covid-caution is completely unique, with some holed up at home for weeks at a time and others traveling the country to visit friends,” Kumi Smith, an epidemiologist at the University of Minnesota, told me over email. “While the institutional level measures may seem extreme, if they had been more uniformly implemented around the country for longer, we might have been able to achieve low enough community transmission to the point that a careful reopening coupled with other measures like contact tracing and widespread testing and isolation would have been possible.”
The paradoxical lesson of flattening the Covid-19 curve is that the concept proved its worth, but it may be more difficult in the future to sell the public on such a strategy.
Nobody disputes the value of slowing transmission in order to relieve pressure on the health system. But it had an expiration date as a motivational tool.
“We know it works. We’ve seen that again and again in this pandemic,” Jen Kates, director of global health policy at the Kaiser Family Foundation, told me. “This will be a standard part of pandemic preparedness and response going forward.”
“An open question, though, will be to what extent has the concept been poisoned by the political discourse?” she added. “How successfully can it be used in the future?”