1. Introduction

The majority of the world’s population lives in cities, which are also engines of economic growth and innovation. On the other side, cities are open to many stressors such as natural and artificial disasters due to their significant concentration of people and activity (Sharifi, 2020). While pandemics had impacted cities before, there is not enough literature on cities and pandemics before the outbreak of the COVID-19 pandemic (Matthew and McDonald, 2006). The previous epidemic has pushed the question of urban pandemic risk to be an exciting subject. Because many factors like climate change and human expansion on natural wildlife habitats may increase the frequency of pandemics in the future, understanding the basic patterns and dynamics of pandemics and their effects on cities is essential (Connolly et al., 2020).

As seen in history, a disease outbreak may happen at any moment, the spread of disease can be quick and tragic. Many people died during the Spanish flu pandemic (1918–1920) than in World War II (Centers for Disease Control and Prevention, 2018). Many pandemics have influenced our history and society; in Figure 1, we can see a timeline of global pandemic outbreaks from ancient times to the twenty-first century (Huremović, 2019).

Survivors of the 1918 pandemic virus have caused almost all seasonal influenza epidemics during the last century; all influenza viruses responsible for the pandemics of 1957, 1968, and 2009. Also, it derived from the founding 1918 virus by gene changing between human, avian, and swine influenza viruses (Morens et al., 2009), as shown in Figure 2.

As several urban forms and design elements can determine pandemic dynamics, the present study has primarily concentrated on density-related aspects; The COVID-19 epidemic brought up questions about the effects of compact urban development. Due to the high level of face-to-face interaction, densely inhabited and well-connected places were thought to be hotspots for the rapid spread of the pandemic. The evidence for a link between density and COVID-19, on the other hand, is diverse and unclear. In a study of over 900 metropolitan counties in the United States (Sharifi and Khavarian-Garmsir, 2020). Unexpectedly, in many studies, they found that high-density areas had slightly lower virus-related mortality rates than broad areas. Willem R. found no significant positive link between county density and infection rate in the Netherlands, which is generally highly urbanized and densely inhabited. Boterman concludes that the public debate focuses on the high risks of infection in cities due to disruptive behaviors when controlling for age and public health factors (Boterman, 2020). On the other side, Lin et al. also discovered that the percentage of the population who came from Wuhan to other metropolitan and population densities are essential factors in explaining the COVID-19 spread rate in China. The highest scaled transmission rates were reported in densely populated urban areas and colder northern Chinese provinces. Disease spread had a non-linear connection with population density as shown in Figure 3 (Lin et al., 2020).

Also, the linear link between population density and spread rate vanished after controlling the first variable, looked at the influence of population density, and found that high spread rates were not found in high-density metropolitan areas (Sharifi and Khavarian-Garmsir, 2020).

As seen in the history of the effect of these epidemics on different aspects of social lives, this study depends on the impact of COVID-19 on our lives today, which started in December 2019, the Coronavirus (COVID-19) erupted in Wuhan, China. By March 2020, the virus had spread around the world. In July 2020, the World Health Organization (WHO) reported that the virus might be transmitted through the air. The virus spreads as quickly and is more deadly than the seasonal flu (World health organization, 2021b). Now, there are significant public health problems caused by air pollution. In comparison, many studies have assessed air pollution and its effect on the risk of respiratory infection by observing the Coronavirus disease dashboard and global carbon emissions map, as shown in Figures 4 and 5. These approximate values on both maps may be relevant in specific locations and potentially during human disease outbreaks.

In principle, scientific advancements have reduced infection risk and mortality related to many infectious diseases and injuries. But also the efforts of the past to control the pollution sources such as public sanitation, factory pollution, and food processing have helped to minimize the risks on urban health (Jackson, 2003).

Therefore, as mentioned in Figure 6, it is essential to highlight the value of city planning and the urban environment to provide people with a safe and healthy environment. The relation between urban elements like buildings, streets, and public spaces dramatically impacts the quality of life (Kibert, 2016). The pedestrian path is one aspect of the design that is currently attracting much attention. According to the Centers for Disease Control and Prevention (CDC), physical inactivity is responsible for up to 23% of all deaths in the United States due to major chronic diseases. Physical inactivity plays a critical role, which increases the risk of many illnesses (Control and Prevention, 1998). The concept of “Lungs of the City” is about integrating an air cleaning system into strategic urban areas to enhance the air quality at the street level. In 2016, the concept’s validity was investigated; this technology can be used in different places, including busy traffic roads, train and bus stations, and even street furniture as shown in Figure 7a (Environmental Nano Solutions, 2016). These air purification systems clean fine dust and pollutants from the polluted city air on the basis of positive ionization as shown in Figure 7c, and the clean air is blown back into the city (AVADA, 2016).

According to these experiences, Environmental Nano Solutions (ENS), in collaboration with the Eindhoven University of Technology, has developed a plan to implement large-scale air purification in parking garages to improve air quality substantially. By installing Aufero’s device shown in Figure 7b in a car park in Cuijk and the city of Weert, the air inside the parking garage is cleaned, and a part of the surrounding city air. The air quality inside the car park in Cuijk improved due to reducing the fine dust concentration by more than 70% (Environmental Nano Solutions, 2016). Also, other studies prove that this device plays a critical role in improving outdoor air quality (Blocken et al., 2016) (Vervoort et al., 2019). It has been shown that the design of cities and urban spaces directly affects human health through air quality and the need for an urban element that should help to purify the air by using the concept of biophilic design. According to the definition of wellness architecture by the global wellness institute, human health, wellbeing, and comfort are the keys of design that create a base rooted in sustainable and regenerative design principles (Global Wellness Institute (GWI), 2017).

According to the World Health Organization (WHO), air pollution causes 4.2 million deaths per year, and 91% of the world’s population lives in areas where air quality fails to meet the recommended standards (World Health Organization, 2021a). In order to design buildings and urban spaces, urban designers can control the spread of disease by designing spaces that promote health-giving features through the circulation of airflow, natural light, and biophilic elements (Garofalo, 2020). To better meet the needs of pedestrians and offer sufficient green and open areas to suit inhabitants’ aspirations for outdoor exercise and enjoyment. Recently, green roofs, made up of grasses, flowers, and other plants, have been popular in city planning. It is an approach that could help in improving the urban thermal environment. In the daytime, less solar radiation is absorbed because of vegetation canopies at a green roof, which is called the shading effect of vegetation (Fioretti et al., 2010). Pollutants can be removed from the air by plants. Because of the increase in environmental pollution, plants’ ability to purify the air has gotten much attention (Li et al., 2010). The different forms of vegetation like trees, shrubs, and grasses have a different proportion of land areas in cities. According to a study in Chicago, the total of annual air pollutants increased by using green roofs; 1675 kg of air pollutants was removed by 19.8 ha of green roofs in one year (Yang et al., 2008).

This paper provides enhancing scenarios for the air quality in urban areas, tested by simulation on a selected site on Aswan, Egypt. The research could serve as a foundation for evaluating recent research by Sharifi’s (2020) recommendations for enhancing pandemic-proof design and policy considering the geographic distribution of Covid-19 mortality. For example, we should focus on greening, the transportation, and manufacturing sectors and increase air pollution reduction (Sharifi and Khavarian-Garmsir, 2020). Also, When the study parameters are combined by A. AbouKorin (2021), they have a considerable impact on COVID-19 spreading. They conclude that the most critical component is the intra-city connectivity provided by public transportation. As a result, and based on research findings, public transportation planning should receive a more significant proportion of future research interest. This is also necessary for a low-carbon, inclusive urban development (AbouKorin et al., 2021). From here, different helpful suggestions for limiting disease spread and reducing crowding were made in this research.

2. Methodology

The methodology of this research is adopted by the following steps displayed in the schematic diagram to achieve the main focus of the study. The adopted steps are shown in Figure 8. To indicate air quality in an urban environment in this research by simulation software, ENVI-met 4.4.5 is used to model the study area as a three-dimensional model and simulate the air quality and the values of carbon emissions within the selected study area. The selected site in Aswan, Egypt, was selected according to its importance, historical background, and effect on the city’s urban form. Moreover, to validate the simulation data, it was needed to record actual values of carbon emission in this area by using CI-340. Furthermore, to achieve the aim of this research, by having strategies to attain improvement and reach a good level of air quality. It suggested enhancing air quality by using algae stations to help purify the air, produce more oxygen, and see its effect simulation using SuperPro Designer software. Also, as an alternative solution, the use of a green roof was tested by simulating its effect using ENVI-met 4.4.5; the results of the two suggested solutions were different from the existing case, which modified the process of enhancing air quality.

3. Study area

The case-study district at Aswan, Egypt, as shown in the location in Figure 10, the case-study covers a 35,492.35 m² area shown in Figure 11, with a built-up area of about 85% and heights between 12–18 m. (Starts from 24°05′25.8′′N 32°53′43.5′′E to 24°05′20.6′′N 32°53′54.6′′E).

This quarter is an important area around a street considered as an artery between the two main streets in Aswan; this street links between Cornish street, the Nile-front in Aswan, and another main street parallel to the Cornish, as seen in Figure 12.

As shown in Figures 13 and 14, This street was not that wide before 2006. It was a residential area filled with buildings and houses. It became wider to solve the problem of slum area, but it caused traffic jam problems. Which affected the environmental quality because of the creation of many air polluting sources and little ventilation; improving air quality, especially in these critical streets in Aswan city, positively influences the residents’ health.

4. Results and discussion

5. Conclusions and future work

The pandemic of COVID-19 impacted negatively on many countries throughout the world in early 2020. Since then, daily life in many cities has been disrupted; the scientific community has been working on casting more insight on the underlying dynamics of the COVID-19 epidemic, which is still wreaking in many world regions. So, it was essential to look for some modifications to enhance the existing urban environment, such as using algae stations and green roofs and test its effect by simulation. The validation between the simulation results and records of carbon emission from the study area proved that the urban environment has a vital role in achieving a safe environment for the users with healthy air quality. The simulation process proved that the use of algae stations as an air purifying system and green roofs in high-density urban blocks could help in the improvement of air quality and reduce the number of carbon emissions, according to the previous studies. More research is needed to improve disease prevention and infection management through urban design. In this research, the evaluation of pandemics’ effects on various urban forms was necessary. Also, suggest key elements that should be considered for better preparation and reaction to such future situations, and indicate gaps that need to be further researched in future research, based on early evidence presented in the literature. It could change the perspective of planners and designers to find new solutions to achieve a safe environment for the users. These characteristics will make the cities ready for any future pandemics, and the suggested guidelines may be followed to reach a sustainable, safe city with good air quality.