New GPS tracking data from 45 million cell phones in the US shows that stay-at-home orders slowed the spread of COVID-19 by three-fold.
The amount of time it took for the number of US coronavirus cases to double was stretched from less than two days to six after more Americans started moving less, University of Wisconsin-Madison researchers found.
As the pandemic took off across the US, 42 states issued stay-at-home orders or advisories in a desperate attempt to slow the spread of the virus.
Much of the country protested the measures as draconian and prohibitive to businesses.
The US economy did indeed reel from sudden sea-change, millions lost their jobs, but the new study leaves little doubt that keping Americans home also kept them safe from infection and reduced the number of coronavirus cases.
A clear ‘flattening’ of the epidemic curve occurred after stay-at-home orders (blue), as measured by the time it took for COVID-19 case numbers to double, University of Wisconsin-Madison research found
At the height of the coronavirus pandemic in the US, the number of new infections nationwide doubled in single week.
In just 6.5 days between March 31 and April 7, the US added 35,000 new cases.
When New York City was the worldwide epicenter of the pandemic, the number of cases in New York state was doubling every two days, as of March 30.
By the second week of April, the number of cases in the city was still rising fairly steeply, but it took eight days for the tally to double.
It was the first glimmer of hope that Governor Andrew Cuomo’s stay-at-home order and intense lockdown of the state was was working.
According to the new study, published in JAMA Network Open, cases in New York were doubling every 1.8 days, on average, prior to the March 20 stay-home order.
After the order, it took an average of 6.4 days for the number of cases in the state to double (up until the end of the study period, April 10).
By April 10, more than 460,000 Americans had tested positive for coronavirus, but after stay-at-home orders, the time it took for cases to double increased from less than three days to six
During that period, the average daily distance travelled by cell phones fell from 2.01 km to 0.04 km per day.
Instead, New Yorkers spent 118.7 minutes longer at home each day, compared to before they were ordered to stay home.
California was the first state in the mainland US to issue a mandatory stay-at-home order, on March 19 (it was beaten by Puerto Rico, which issued its mandate four days earlier).
At the time, the state had 1,040 confirmed cases of coronavirus, and 19 people had died.
Much of the country balked at Democratic Governor Gavin Newsom’s order. Some called it draconian, others regarded it as an over-reaction to a virus that had, at the time, infected less than 0.003 percent of California’s population.
After stay-at-home orders or advisories were issued in 42 states, the distance Americans traveled decreased (top) and their time at home increased (bottom)
The time it took for case numbers to double in the state stretched from 3.3 days to 5.3 days over the course of the study. The difference may have been less dramatic because the order was issued so early, heading off exponential case increases.
But in the months that followed, 41 other states enacted measures similar to California’s.
Another eight states issued advisories urging residents to stay home, but did not create enforceable policies.
Six states – Arkansas, Nebraska, North Dakota, South Dakota, Utah and Wyoming – did nothing to limit contact and movement.
Those states are far less densely populated than coastal ones like California or New York, and even now they have a fraction as many cases.