Arizona's COVID-19 Cases After Mask Mandates and Closures, 2020

This report covers the first months of the COVID-19 pandemic in 2020, before vaccines or widely available treatments.

Slowing the spread of SARS-CoV-2, the virus that causes COVID-19, takes action by individuals, communities and states. Community mitigation measures include wearing masks, keeping physical distance, limiting large gatherings, pausing businesses where distancing is hard, working or staying at home, and controls in workplaces and schools. The Arizona Department of Health Services (ADHS) based its recommendations on continual monitoring of patients, community spread and the strain on hospitals. To judge whether those measures worked, ADHS compared daily case counts and 7-day averages from January 22 to August 7, 2020, with the timing of each step.

The timeline

Local enforcement varied by county and city and included educating people about the dangers of spread, fining people and businesses that refused to comply, and pulling licenses from businesses that did not enforce the rules. The June measures were extended through August.

What happened to cases

• Peak: the 7-day average of daily cases peaked from June 29 to July 2, at 4,148 to 4,377.
• Plateau: it held steady from July 3 to 12, at 3,609 to 4,160, about two weeks after mask mandates and enhanced sanitation began.
• Decline: it then fell 75%, from 3,506 on July 13 to 867 on August 7, as statewide limits and closures stayed in place.

What the authors concluded

Hard data on how well community measures suppress COVID-19 were scarce. Arizona's main goal was to save lives and keep the health system from being overwhelmed. Combining voluntary and enforceable measures works better than any single step, policies can increase distancing, and masks had been shown to prevent transmission. In Arizona, cases fell after sustained measures that promoted distancing, limited large gatherings, paused businesses where masks and distancing were hard to maintain, required and enforced masks, and encouraged people to stay home and wear masks where they were not required.

The authors urged communities and individuals to use such measures to slow COVID-19, especially until a vaccine or treatment became widely available, with state, local and tribal officials monitoring data together to decide what level of measures was needed. Mask mandates and other measures, implemented and enforced across the state, appear to have been effective in reducing spread in Arizona.

Limits

• The link between the measures and the case trends is a timing correlation, not proof of cause. Travel restrictions, neighboring states' measures and people's own choices to stay home earlier may also have played a part.
• Tribal health centers and federal facilities (the Indian Health Service, the Veterans Administration and the Department of Defense) are asked, but not required, to follow state reporting rules; many did, but how completely is unknown.
• How well people followed the measures was not assessed, and the effect of each measure could not be separated.
• Arizona may not represent other states, especially larger or more densely populated ones.

Sources

• Gallaway MS, Rigler J, Robinson S, et al. Trends in COVID-19 Incidence After Implementation of Mitigation Measures — Arizona, January 22–August 7, 2020. MMWR Morb Mortal Wkly Rep 69(40); posted as an Early Release on October 6, 2020. https://www.cdc.gov/mmwr/volumes/69/wr/mm6940e3.htm
• The report was written by the Arizona Department of Health Services with CDC; its figure and social media graphic are not reproduced here.