Public policies to increase compliance with community mitigation strategies may be effective in decreasing community mobility.
The CDC’s Morbidity and Mortality Report suggests that public policy measures are an important tool to support social distancing. The report also provides some early indications that these measures might help slow the spread of coronavirus disease 2019 (COVID-19).
Previous studies have found that implementing community mitigation strategies, including personal protective measures such as handwashing and cough etiquette, social distancing, and environmental cleaning in community settings, can slow the spread of infections during a pandemic.
The CDC report presents initial data from 4 studied metropolitan areas—San Francisco, Seattle, New Orleans, and New York City—that describe the relationship between timing of public policy measures, community mobility (a proxy measure for social distancing), and temporal trends in reported COVID-19 cases. According to the report, community mobility in all 4 locations declined from February 26, 2020 to April 1, 2020, decreasing with each policy issued, and as case counts increased.
When a novel virus with pandemic potential emerges, community mitigation strategies often are the most readily available interventions to slow transmission. CDC-recommended community mitigation interventions for COVID-19, caused by the SARS-CoV-2 virus, are based on evidence for other viral respiratory illnesses and emerging data on SARS-CoV-2 transmission and epidemiology, including groups at highest risk for hospitalization and death from COVID-19.
Public policies to implement social distancing include emergency declarations, bans on gatherings of certain sizes, school closures, restrictions on businesses, and safety-at-home or shelter-in-place of residence orders.
According to the report, since these strategies can substantially disrupt daily life, their implementation should align with the progression and severity of disease. Understanding the timing and potential impact of policies designed to increase compliance with mitigation strategies will help guide modification of policies over the course of the COVID-19 pandemic as well as increasing the understanding of when and how to fully implement these strategies in future outbreaks where community mitigation is required.
Researchers examined data from February 26-April 1, 2020 from the 4 studied metropolitan areas, which were selected because each had substantial numbers of reported COVID-19 cases during the early stages of the United States epidemic. Researchers analyzed the types and timing of public policies issued to promote community mitigation interventions at the national, state, and local government levels, cumulative number of reported COVID-19 cases, average 3-day percentage change in reported cases, and community mobility.
In each of the 4 locations, a combination of state and local community mitigation policies was issued, and all 4 metropolitan areas were in states that declared a state of emergency and put local limits on mass gatherings, although these varied by number of people allowed and, in some cases, changed over time. Additionally, all 4 areas issued school closure and stay-at-home orders at state or local levels, and 3 parishes in the New Orleans region were the only areas in this study to implement a curfew.
Timing of community mitigation policies in relation to the increasing cumulative case counts of COVID-19 varied by location. In all 4 metropolitan areas, an emergency declaration was the first policy issued, before large increases in cumulative cases, while stay-at-home orders were the last mitigation policy to be issued. In all 4 metropolitan areas, the percentage of residents leaving home declined as the number of policies issued increased. Overall, across the 4 areas, emergency declarations did not result in a sustained change in mobility; however, declines in mobility occurred after implementation of combinations of policies, and after the White House 15 Days to Slow the Spread guidelines were implemented.
During February 26, 2020—April 1, 2020, as cumulative cases increased and community mitigation policies were implemented, community mobility declined in the 4 studied US metropolitan areas. With the exception of emergency declarations, which were implemented as cases increased in other regions and internationally, these policies were implemented during the period when case counts were increasing in each location, but the timing in relation to cumulative case counts varied.
Timing of Community Mitigation and Changes in Reported COVID-19 and Community Mobility. CDC website. Morbidity and Mortality Weekly Report. Published April 13, 2020. https://www.cdc.gov/mmwr/volumes/69/wr/mm6915e2.htm?s_cid=mm6915e2_e&deliveryName=USCDC_921-DM25761. Accessed April 13, 2020.