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. 2020 Jul 8:1-10.
doi: 10.14218/ERHM.2020.00045.

Associations of Stay-at-Home Order and Face-Masking Recommendation with Trends in Daily New Cases and Deaths of Laboratory-Confirmed COVID-19 in the United States

Jie Xu  1 , Sabiha Hussain  2 , Guanzhu Lu  1 , Kai Zheng  3 , Shi Wei  4 , Wei Bao  5 , Lanjing Zhang  6   7   8   9
Affiliations

Associations of Stay-at-Home Order and Face-Masking Recommendation with Trends in Daily New Cases and Deaths of Laboratory-Confirmed COVID-19 in the United States

Jie Xu et al. Explor Res Hypothesis Med. .

Abstract

Background and objectives: Public health interventions have reduced coronavirus disease 2019 (COVID-19) transmission in several countries, but their impacts on COVID-19 epidemics in the USA are unclear. We examined associations of stay-at-home order (SAHO) and face-masking recommendation with COVID-19 epidemics in the USA.

Methods: In this quasi-experimental interrupted time-series study, we modeled temporal trends in daily new cases and deaths of laboratory-confirmed COVID-19 cases, and COVID-19 time-varying reproduction numbers in the USA between March 1 and April 20, 2020. In addition, we conducted simulation analyses.

Results: The number of residents under SAHO increased since March 19 and plateaued at 290,829,980 (88.6% of the U.S. population) on April 7. Trends in COVID-19 time-varying reproduction numbers peaked on March 23, further reduced on April 3, and fell below/around 1.0 on April 13. Early-implementation and early-lift of SAHO would reduce and increase COVID-19 epidemics, respectively. Multivariable piecewise log-linear regression revealed the states' neighboring relationship with New York was linked to COVID-19 daily new cases and deaths. There were two turning points in daily new-case trend, being March 28 (slope-changes = -0.09) and April 3 (slope-changes = -0.09), which appeared to be associated with implementation of SAHO on March 28 (affecting 48.5% of the US population in 22 states and District of Columbia), and face-masking recommendation on April 3, respectively. There were also two turning points in daily new-death trend, being April 9 (slope-changes = -0.06) and April 19 (slope-changes = -0.90).

Conclusions: We identified two turning points of COVID-19 daily new cases or deaths in the USA, which seem to be linked to implementation of SAHO and the Center for Disease Control's face-masking recommendation.

Keywords: COVID; Coronavirus disease 2019; Face-masking; Incidence; Policy; Trend.

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Conflict of interest statement

No disclosures were reported.

Figures

Fig. 1
Fig. 1. The population under a stay-at-home order (SAHO) owing to the COVID-19 in the USA.
Since March 19, 2020, when the state of California started a SAHO, the number and proportion of the USA residents under SAHO increased until April 7 and plateaued afterwards.
Fig. 2
Fig. 2. Observed and simulated trends in daily new cases and deaths of laboratory-confirmed COVID-19 in the USA between March 1 and April 30, 2020.
The Joinpoint analyses with Poisson variance model shows that the two turning points of March 23 and April 3 divided the trends in USA COVID-19 daily new cases into three segments, with the coefficients of 31.69 (95% CI of 26.82 to 36.75, p < 0.001), 9.75 (95% CI of 7.54 to 12.01, p < 0.001), and −0.90 (95% CI of −1.62 to −0.17, p = 0.02), respectively. These turning points appeared to link to implementation of a SAHO by 10 states on March 23, and the CDC’s face-masking recommendation on April 3. Similarly, the two turning points of April 3 and April 15 divided the trends in USA COVID-19 daily new deaths into three segments, with the coefficients of 25.06 (95% CI of 21.44 to 28.79, p < 0.001), 5.22 (95% CI of 3.36 to 7.11, p < 0.001), and −7.90 (95% CI of −13.45 to −1.99, p = 0.01), respectively. The simulated results on early-implementations of SAHO and face-masking recommendation and early-lift of SAHO are shown in A and C, and B and D, respectively, in a form removing a portion or all of the slope changes attributable to SAHO (denoted as removal of SAHO’s coefficient(ß) in the figure).
Fig. 3
Fig. 3. Estimated effective Rt based on laboratory-confirmed COVID-19 cases in the USA and the reported serial intervals.
The effective Rt was estimated using the previously-reported COVID-19 mean serial-intervals (SI) of 7.5 (A), 4.7 (B) and 3.96 (C) days, as well as the corresponding standard deviations (SDs). The statewide SAHO was first implemented by the state of California on March 19, 2020 (yellow dashed line). Ten states had implemented a SAHO by March 23, 2020 (green dashed line), affecting 114,047,753 residents (37.45% of the U.S. population). The CDC recommended face-masking on April 3, 2020 (blue dashed line). These dates were linked to the declines in Rt’s at the times of an increase or plateau of the Rt.
Fig. 4
Fig. 4. Observed trends in daily new cases and deaths of laboratory-confirmed COVID-19 by state neighboring relationship with New York in the USA between March 1 and April 30, 2020.
The daily new cases (A) and new deaths (B) of COVID-19 were higher in New York than in the six neighboring states of New York (Connecticut, Massachusetts, New Jersey, Pennsylvania, Rhode Island, and Vermont), and higher in the neighboring states than other non-New York states (p < 0.001 for both). The lines were smoothed using a locally weighted scatter smoothing (known as LOWESS) algorithm.
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