Evidence that early social distancing policies saves lives — Columbia model

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If the US had begun imposing social distancing measures one week earlier than it did in March, about 36,000 fewer people would have died in the coronavirus outbreak. The New York Times reports that this is according to new estimates from Columbia University disease modelers that also found if the country had begun locking down cities and limiting social contact on 1 March, two weeks earlier than most people started staying home, the vast majority of the nation’s deaths – about 83% – would have been avoided, the researchers estimated.

Under that scenario, about 54,000 fewer people would have died by early May. The enormous cost of waiting to take action reflects the unforgiving dynamics of the outbreak that swept through American cities in early March. Even small differences in timing would have prevented the worst exponential growth, which by April had subsumed New York City, New Orleans and other major cities, the researchers found.

“It’s a big, big difference. That small moment in time, catching it in that growth phase, is incredibly critical in reducing the number of deaths,” said Jeffrey Shaman, an epidemiologist at Columbia and the leader of the research team.

The findings are based on infectious disease modelling that gauges how reduced contact between people starting in mid-March slowed transmission of the virus. Shaman’s team modelled what would have happened if those same changes had taken place one or two weeks earlier and estimated the spread of infections and deaths until 3 May.

The results show that as states reopen, outbreaks can easily get out of control unless officials closely monitor infections and immediately clamp down on new flare-ups. And they show that each day that officials waited to impose restrictions in early March came at a great cost.

After Italy and South Korea had started aggressively responding to the virus, President Trump resisted cancelling campaign rallies or telling people to stay home or avoid crowds. The risk of the virus to most Americans was very low, he said.

“Nothing is shut down, life & the economy go on,” Trump tweeted on 9 March, suggesting that the flu was worse than the coronavirus. “At this moment there are 546 confirmed cases of coronavirus, with 22 deaths. Think about that!”

The report says in fact, tens of thousands of people had already been infected by that point, researchers later estimated. But a lack of widespread testing allowed those infections to go undetected, hiding the urgency of an outbreak that most Americans still identified as a foreign threat.

In a statement released late Wednesday night in response to the new estimates, the White House reiterated Mr. Trump’s assertion that restrictions on travel from China in January and Europe in mid-March slowed the spread of the virus.

On 16 March, Trump urged Americans to limit travel, avoid groups and stay home from school. Bill de Blasio, mayor of New York City, closed the city’s schools on 15 March, and Governor Andrew Cuomo issued a stay-at-home order that took effect on 22 March. Changes to personal behaviour across the country in mid-March slowed the epidemic, a number of disease researchers have found.

But in cities where the virus arrived early and spread quickly, those actions were too late to avoid a calamity.

All models are only estimates, and it is impossible to know for certain the exact number of people who would have died. But Lauren Ancel Meyers, a University of Texas at Austin epidemiologist who was not involved in the research, said that it “makes a compelling case that even slightly earlier action in New York could have been game changing.”

“This implies that if interventions had occurred two weeks earlier, many COVID-19 deaths and cases would have been prevented by early May, not just in New York City but throughout the US,” Meyers said.

Abstract (pre-print)
Assessing the effects of early non-pharmaceutical interventions1-5 on COVID-19 spread in the United States is crucial for understanding and planning future control measures to combat the ongoing pandemic6-10. Here we use county-level observations of reported infections and deaths11, in conjunction with human mobility data12 and a metapopulation transmission model13,14, to quantify changes of disease transmission rates in US counties from March 15, 2020 to May 3, 2020. We find significant reductions of the basic reproductive numbers in major metropolitan areas in association with social distancing and other control measures. Counterfactual simulations indicate that, had these same control measures been implemented just 1-2 weeks earlier, a substantial number of cases and deaths could have been averted. Specifically, nationwide, 61.6% [95% CI: 54.6%-67.7%] of reported infections and 55.0% [95% CI: 46.1%-62.2%] of reported deaths as of May 3, 2020 could have been avoided if the same control measures had been implemented just one week earlier. We also examine the effects of delays in re-implementing social distancing following a relaxation of control measures. A longer response time results in a stronger rebound of infections and death. Our findings underscore the importance of early intervention and aggressive response in controlling the COVID-19 pandemic.

Authors
Sen Pei, Sasikiran Kandula, Jeffrey Shaman

Full The New York Times report

Columbia University estimates

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