Americans Social Distanced Before They Were Told to, and It Potentially Saved Others

People in the U.S. who started social distancing due to the COVID-19 pandemic before being advised to by leaders likely saved lives, according to a study.

In the four months after the first COVID-19 case was reported in the U.S. on January 20, 2020, the coronavirus had spread to every state and over 90 percent of all counties, according to the authors of the paper published in the journal The Lancet. The response from leaders during this period was "highly decentralised," the researchers said, and stay-at-home orders varied in different states and localities.

To investigate whether people's behavior affected the spread of the coronavirus, the researchers looked at anonymized cell phone data reflecting movement in each U.S. county, between January 1 to April 20. They also took into account the number of COVID-19 cases for a given county on a given day. The team took a drop in the frequency of trips as an indicator that individuals were social distancing.

This enabled them to use statistical models to estimate how social distancing affected the rate of new infections in the 25 counties that the highest number of confirmed cases on April 16, 2020. These were Essex, Hudson, Union, Bergen, Passaic, Middlesex, and Monmouth in New Jersey; New York's New York City, Nassau, Suffolk, Westchester, Rockland, and Orange; Cook, Illinois; Middlesex and Suffolk, Massachusetts; Miami-Dade, Florida; Philadelphia, Pennsylvania; Wayne and Oakland, Michigan; Jefferson and Orleons, Louisiana; Los Angeles, California; Fairfield, Connecticut, and Harris, Texas.

A strong link emerged between patterns of less movement and drops in the growth of COVID-19 cases for the counties. Due to the incubation period of the virus, there was a lag of up to three weeks before changes in movement were reflected in the COVID-19 cases.

In "many" U.S. counties, people appeared to change their behavior days to weeks before they were advised to do so by state or local authorities, the researchers wrote. This indicates that people anticipated the recommendations, "despite a mixed political message."

In every county, except for Jefferson, local directives were put in place at least 3 - 17 days before state-level stay-at-home orders.

The team said the study showed that social distancing which slowed the growth of outbreaks in the counties was largely driven by individuals and regulations on a local level. "The state (and federal) actions were implemented either too late (or not at all)," they said.

More research is needed to uncover why people chose to take fewer trips, but it could be due to educational and data-tracking resources, as well as media and the sharing of information, according to the study.

"These findings show that it is within the power of each U.S. resident, even without government mandates, to help slow the spread of COVID-19," the authors wrote.

"Crucially, if individual-level and local actions were not taken, and social distancing behavior was delayed until the state-level directives were implemented, COVID-19 would have been able to circulate unmitigated for additional weeks in most locations, inevitably resulting in more infections and deaths," they said.

The study had a number of limitations, including that it focused on movement and the rate of growth of cases, and therefore didn't measure others factors that could affect the spread of infection, like mask-wearing and handwashing. Also, the team didn't know how high-risk the trips people took were, for instance going to the park alone versus visiting the grocery store. In addition, the study only focused on 25 counties.

Co-author Lauren Gardner, co-director of the Center for Systems Science and Engineering at Johns Hopkins, said in a statement: "Our results strongly support the conclusion that social distancing played a crucial role in the reduction of case growth rates in multiple U.S. counties during March and April, and is therefore an effective mitigation policy for COVID-19 in the United States."

Co-author Hamada Badr, a research scientist in the Department of Earth and Planetary Sciences at Johns Hopkins, said: "As stay-at-home policies began to relax, we urge individuals and governments to make safe and data-driven decisions, to respond to the potential risk of increased infections. More timely, consistent and decisive policy implementation of social distancing and other known effective mitigation measures is urgently needed."

The study comes amid a rise in COVID-19 cases in the U.S., particularly in the South and West. The country already leads the world in diagnoses at over 2.6 million of the 10.7 million cases worldwide, according to Johns Hopkins University.

COVID19, coronavirus, getty
Shoppers social distance themselves as they wait in line to get into Costco in Washington, DC, on April 5, 2020. JIM WATSON/AFP via Getty Images