The Effect of Stay-at-Home Orders on COVID-19 Infections in the United States

James H. Fowler; Seth J. Hill; Nick Obradovich; Remy Levin

Coronavirus disease 2019 (COVID-19) first appeared as a cluster of pneumonia cases in Wuhan, China on December 31, 2019 1 and was declared a global pandemic by the World Health Organization (WHO) on March 11, 2020. 2 As of April 17, 2020, the European Centers for Disease Control reports that worldwide there have been 2,114,269 confirmed cases of COVID-19, resulting in 145,144 deaths. 3 The United States recently became the country with both the highest number of cases (671,331) and deaths (33,284) due to the disease. 3 As a result, the U.S. government has been widely criticized for inaction in the early stages of the pandemic. 2 Although the first confirmed case of COVID-19 was reported to the Centers for Disease Control on January 21, 2020 and documented transmission commenced immediately, 4 a national state of emergency was not declared until nearly two months later on March 13. At that time, no mandatory actions were ordered at the national level other than international travel restrictions. 5 While the national government has the authority to act, the United States is a federal political system where public health is normally the purview of the fifty states. Furthermore, each state often delegates health authority to cities and/or counties, geographic political units nested within states. As a result, responses to COVID-19 varied across states and counties and led to spatial and temporal variation in implementation of mitigation procedures. This variation in policy responses has likely contributed to significant variation in the incidence and growth of infections across jurisdictions in the United States. 6 A variety of government policies have been proposed and used to mitigate the spread and consequence of pandemic diseases like COVID-19, ranging from investments in medical testing, contact tracing, and clinical management, to school closures, banning of mass gatherings, quarantines, and population stay-at-home orders. 7 China's extensive interventions appear to have been successful at limiting the outbreak. 8, 9 These include quarantines both for those diagnosed and those undiagnosed but who had been in Hubei province during the outbreak, 10 and restrictions on travel to and from affected areas. 11 In contrast, school closures across East Asia were estimated to be much less effective. 12 With estimates that nearly half of transmissions occur from pre-symptomatic and asymptomatic individuals, epidemiological simulations suggest that quarantines of symptomatic individuals alone will be insufficient to halt the pandemic. 13 This has led to widespread adoption of population-wide policies to dramatically reduce social contact.