In the United States, more than one million coronavirus cases and over 59,000 deaths could have been prevented by early May had social distancing been implemented two weeks sooner, revealed study published in the journal Science Advances.
"Our results demonstrate the dramatic impact that earlier interventions could have had on the COVID-19 pandemic in the US," the authors wrote.
Seeking to understand the impact of timing when implementing non-pharmaceutical interventions, Sen Pei from Columbia University in New York and colleagues first built a metapopulation model of Covid-19 transmission in all 3,142 US counties during the period spanning February 21 through May 3.
The model revealed notable yet asynchronous reductions in disease transmission rates, reflected in changes to the estimated effective basic reproduction number (Re) in most counties during this time period.
They then performed counterfactual simulations with the same model, moving the timing of non-pharmaceutical interventions implementation either one week or two weeks sooner.
In the first model, advancing non-pharmaceutical interventions by a week, to March 8, resulted in 601,667 fewer confirmed cases and 32,335 fewer deaths nationwide as of May 3.
In the second model, implementing NPIs a full two weeks earlier, on March 1, resulted in over one million fewer confirmed cases and 59,351 fewer deaths.
The researchers acknowledged that their modeling simplifies some assumptions related to general uncertainty, economic concerns, administrative decision-making, and public adherence to social distancing rules.
However, they also pointed to continuing successes in countries such as South Korea, New Zealand, Vietnam, and Iceland that did implement non-pharmaceutical interventions in early March.
Over 9.7 million people in the US have tested positive for Covid-19 so far, while more than 236,000 have died, according to data from Johns Hopkins University.