Many Americans decided to start physical distancing even before statewide stay-at-home orders were issued, likely helping slow transmission of COVID-19 in the 25 hardest-hit counties, a modeling study published yesterday in The Lancet Infectious Diseases has found.Using mobile phone data from Jan 1 to Apr 20, researchers at Johns Hopkins University identified a decline in the number of daily trips people made 6 to 29 days before states mandated that residents stay home to slow the spread of the novel coronavirus.
After establishing a baseline of normal movement from Jan 8 to 31, they looked for changes through Apr 17 and assessed epidemiologic data on COVID-19 cases for each county.Regional variation in extent of physical distancingThe