Prevalence of unmasked and improperly masked behavior in indoor public areas during the COVID-19 pandemic: Analysis of a stratified random sample from Louisville, Kentucky.

Seyed M Karimi,Dylan M Hurst,Riten Mitra,Sonali S Salunkhe,Caleb X He,Devin N Swinney,W Paul Mckinney,Kelsey B White,Emmanuel Ezekekwu,Bert B Little,Emily R Adkins,Sarah S Moyer,Martha M Popescu,Natalie C Dupré,David A Johnson,Julia A Barclay,Rebecca Hollenbach,Yuting Chen,Cosme F Buzzachera

doi:10.1371/journal.pone.0248324

Abstract

Wearing a facial mask can limit COVID-19 transmission. Measurements of communities' mask use behavior have mostly relied on self-report. This study's objective was to devise a method to measure the prevalence of improper mask use and no mask use in indoor public areas without relying on self-report. A stratified random sample of retail trade stores (public areas) in Louisville, Kentucky, USA, was selected and targeted for observation by trained surveyors during December 14-20, 2020. The stratification allowed for investigating mask use behavior by city district, retail trade group, and public area size. The total number of visited public areas was 382 where mask use behavior of 2,080 visitors and 1,510 staff were observed. The average prevalence of mask use among observed visitors was 96%, while the average prevalence of proper use was 86%. In 48% of the public areas, at least one improperly masked visitor was observed and in 17% at least one unmasked visitor was observed. The average prevalence of proper mask use among staff was 87%, similar to the average among visitors. However, the percentage of public areas where at least one improperly masked staff was observed was 33. Significant disparities in mask use and its proper use were observed among both visitors and staff by public area size, retail trade type, and geographical area. Observing unmasked and improperly masked visitors was more common in small (less than 1500 square feet) public areas than larger ones, specifically in food and grocery stores as compared to other retail stores. Also, the majority of the observed unmasked persons were male and middle-aged.

Highlights

Transmission of respiratory viral infections like COVID-19 can be reduced considerably by using a facial mask, especially in indoor public areas [1,2,3,4,5,6,7,8]
The smallest number of public areas (PAs) were observed in the North West district (n = 32, 8%) (S2 Fig in S1 File); the district included 11% of the city’s population (S4 Table in S1 File)
This study was conducted to estimate the prevalence of mask use and improper mask use in indoor public areas of the city of Louisville, Kentucky (USA) in December 2020 and to explore potential patterns in mask-wearing behavior

Summary

Introduction

Transmission of respiratory viral infections like COVID-19 can be reduced considerably by using a facial mask, especially in indoor public areas [1,2,3,4,5,6,7,8]. Many governors within the United States implemented executive orders requiring masks within public indoor areas throughout 2020 [9]. The state of Kentucky mandated public masking on July 9th, 2020, and in March 2021 renewed the executive order until at least July 2021 [10, 11]. When non-interventional observations of mask use replace self-reporting, non-representative sub-populations (e.g., university students and clinic population) have been studied [19,20,21]. Observational studies that do not focus on a specific sub-population or improper masking are scarce [22]. A study conducted in Wisconsin, USA, in summer 2020 approximated a 6% improper mask-wearing rate before the state’s store mask mandate and suggested it decreased to 3% with a store mandate [23]

Methods

Results

Discussion

Conclusion