Background

On December 31, 2019, China reported to the World Health Organization (WHO) a cluster of pneumonia cases of unknown etiology in Wuhan city, Hubei province [1]. The outbreak spread quickly, with an increasing number of cases reported worldwide [2]. In February 2020, the WHO designated the disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) as coronavirus disease (COVID-19) [1]. More than 280,000,000 COVID-19 confirmed cases and 5,000,000 deaths worldwide were reported by the end of 2021, of which more than 700,000 confirmed cases and 150,000 deaths were reported in Africa [3].

In Mozambique, the first case of COVID-19 was registered on March 22, 2020 and by October 30 the same year there were 12,777 confirmed cases and 91 deaths registered [4]. To control the disease’s spread in Mozambique, a 30-day State of Emergency was declared on March 31, 2020. This declaration was extended for two additional months [5]. On September 7, 2020 a State of Public Disaster was declared, which remained in effect during the conduct of this study [6]. This State of Public Disaster required compliance with hand hygiene, physical distancing and the use of masks for the prevention and control of COVID-19.

According to the WHO, the use of masks is part of a comprehensive package of prevention and control measures that can limit the spread of certain viral respiratory diseases, including COVID-19 [7]. The types of masks recommended by the WHO are surgical masks, N95 masks, and non-medical or homemade masks [8]. One study conducted in the United States of America found that mandating face mask use in public was associated with a 2.0 percentage point decline in the daily COVID-19 cases growth rate 21 or more days post implementation [9]. In another large time-interrupted series study in Melbourne, has shown that the reduction of COVID-19 was about 30% depending on the assumptions about serial interval time [10].

A pilot study on mask-wearing behavior in the city of Maputo, Mozambique carried out by Eduardo Mondlane University in February 2020 found that many people (72,9%) were observed wearing masks [11]. However, among those using masks there were still individuals who did not use the masks correctly (27,1%), and that claimed the use of masks caused allergy or difficulty breathing, especially for people with respiratory problems [11]. In Mozambique, the use of masks is mandatory in all public and private transport as well as in all agglomerations of people [12].

With the State of Public Disaster decreed in the country and the start of a more protracted, higher second wave of cases, there was a need to re-assess the use of masks. The aim of the study was to evaluate the use of masks in the prevention of COVID-19, in Maputo City from October 19 to 28, 2020.

Methodology

Results

During the study period, a total of 49,404 individuals were observed; 50.6% were male, 94.1% were adults >18 years of age, and 35.5% were observed in community markets (Table 1).

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Table 1. Distribution of people observed by age group, sex and place of observation (n = 49,404) in evaluation of mask use in public places in the context of COVID-19, 19 to 28 October 2020, Maputo City, Mozambique.

https://doi.org/10.1371/journal.pone.0288957.t001

Distribution of mask use

Regarding mask use, 84.6% of those observed used a mask, of whom, 50.4% were females and 49.5% were males. Mask use was lowest among children (4.8% wore a mask); 95.2% of adults wore masks. In urban areas 96.1% of people observed wore masks and 3.9% wore them in peri-urban areas. Regarding the place of observation, 36.0% of the individuals who used the mask were observed in the market, followed by the supermarket with 32.0% (Table 2).

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Table 2. Distribution of mask use (N = 49,404) in public places, from 19 to 28 October 2020 Maputo City, Mozambique.

https://doi.org/10.1371/journal.pone.0288957.t002

Correct mask use

Of the 41,786 people who used masks, 33,851 (81.0%) used them correctly. Of these, 95.3% were adults, 50.6% were male, 61.7% were observed in the morning, 96.8% were located in urban areas.

The correct use of the mask was 36.3% in markets, and 32.9% in supermarkets. The fabric mask was the most used correctly with 78.9%. Of the 7,935 people who used the mask incorrectly, the most frequent misuse was not covering the mouth and nose, observed in 58.6% of pelople (Table 3).

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Table 3. Proper mask use among mask wearers (N = 41,786) observed from 19 to 28 October 2020, Maputo City, Mozambique.

https://doi.org/10.1371/journal.pone.0288957.t003

Factors associated with the incorrect use of masks

In multivariable regression analysis, the factors significantly associated with incorrect mask use were being female (adjusted Odds Ratio, aOR = 1.2 [1.1–1.3] p <0.001), being observed in peri-urban versus urban areas (aOR = 1.9 [1.8–2.1] p <0.001), and afternoon versus morning observation period/time (aOR = 1.5 [1.5–1.6] p <0.001) (Table 4).

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Table 4. Factors associated with the incorrect use of the masks in public places, Maputo City, 19 to 28 October 2020.

https://doi.org/10.1371/journal.pone.0288957.t004

Discussion

The use of face masks is an effective means to prevent and contain the spread of COVID-19 [14]. This study evaluated the use of face masks in the capital of Mozambique during the COVID-19 pandemic in October of 2020. The majority, 84.6%, of the observed individuals used masks. Similar results were found in a pilot study on mask-wearing behavior in the city of Maputo, where 72% of those observed wore a mask and another study on Adherence to COVID-19 Preventive Measures in Mozambique, where adherence rates were 90% [11, 15].

This study included observations in different locations that provide valuable evidence in public areas with high population density that might represent high transmission risk. Most of those observed were in the markets where the greater concentration and flow of people could create a favorable environment for the transmission of COVID-19, indicating the importance of preventive measures in these settings.

Masks provide protection to the user when used correctly [15, 16]. Although most people observed used their masks correctly, there were also individuals who used them incorrectly, most frequently leaving their nose and mouth uncovered. This fact may be related to the discomfort associated with the length of use of the mask as other studies have revealed that 22.0% of mask removals were due to discomfort and prolonged use, for example sweating or difficulty breathing [16, 17].

The odds of incorrect use were significantly higher among women, in peri-urban areas and during the afternoon period. Women were slightly more likely to use a mask than men, but their significantly poorer likelihood of correct use is indicative of a need for more targeted messaging on how to correctly use masks. Those in peri-urban areas were less likely to use a mask at all and were significantly less likely to have correct mask use which highlights the need for broadening the scope of communication campaigns outside of urban areas where mask use may be worse.

Cloth masks were the type of masks used most frequently by observed individuals. This may be due to this type of masks’ availability, low cost, and possibility of reuse after washing. The use of multi-layer cloth masks is a simple, economical and sustainable alternative to surgical masks as a means of source control for general community use, as is strongly supported by the evidence [18]. Fabric masks may be less fitted than N95 masks and, in turn, have less impact on breathing [19, 20]. Additionally, there have been arguments that for the population to have access to a mask, it was necessary that it be a low-cost one [21], underscoring the value of reusable, inexpensive cloth masks such as those frequently observed in this study. However, these masks are not without some concern as at least one randomized trial found a higher rate of respiratory infections in the group using a cloth mask versus those with surgical masks [22]. Nonetheless, a follow-up study found cloth masks provided equal protection to medical masks for healthcare workers when laundered by the hospital. Additionally, research carried out in Nepal showed that the effectiveness of fabric masks is reduced by 20.0% after the fourth washing and drying Optical microscopic study [20]. Despite these potential concerns related to cloth masks, the lower impact on breathing, lower costs, and higher availability may have contributed to the fact that these were the most frequently documented masks in this study. As such, communication efforts might be most effective if they use imagery of cloth masks and focus on promotion of the correct and consistent use of such masks.

While this study provides valuable insights into frequency and type of mask use in Maputo City, it has some important limitations. These include limitations based on the observational methods which limited assessment of the quality or materials used for the masks, the required estimations of ages and the availability of data that could help illustrate the underlying reasons for any statistically significant differences in correct mask use between groups. Additionally, during data collection a subgroup for the elderly was not categorized, limiting our insight into how mask use may vary in this more vulnerable population.

This study did not include rural areas and other congregated environments and it utilized convenience sampling to help provide data on trends in mask use over time. Each person was only observed over a short time period, so we could not measure consistency of mask use at individual-level. Because the period of observation was brief, the unweighted estimates from this study provide a snapshot of use during the specific regulatory and transmission context that continues to rapidly evolve, underscoring the value of repeating this exercise over time and in more geographic settings.

Conclusions and recommendations

The public observed in urban and peri-urban Maputo City, Mozambique used masks to prevent COVID-19 transmission, however, some individuals used them incorrectly. Incorrect use of masks was associated with being female, living in a peri-urban area and being observed in the afternoon. Intensified public awareness of the correct use of face masks is recommended, especially in peri-urban areas and in the afternoon. Additionally, there is value in continuous monitoring and enforcement of compliance with the rules for wearing masks for the prevention of COVID-19 in public places.

Supporting information

Acknowledgments

The authors would like to thank all who contributed to the planning, implementation, analysis and dissemination of this study, including the coordination of Mozambique Field Epidemiology Training Program, members of the Health System Program at National Institute of Health (including Carlos Botão and Isabel Cambe for their valuable inputs in implementing this second round), the President’s Malaria Initiative, and the Municipality of Maputo City. In addition, we would like to Zandile Nukeri, Beatriz Nhantumbo, Eduardo Chicanequisso, Fabião Mausse, Neusa Fataha, Salomé Mabumo, Cídia Francisco Hermínia Capite and Manuel Paulo for their support in the study implementation.