The aim of the study, the results of which were presented in an article titled. "Cities in the epidemic, the epidemic in cities: Reconstruction of COVID-19 development in Polish cities," published in the journal Cities, was to (1) determine the course of the infection process and its variation over time in selected Polish cities, (2) classify the cities studied due to the similarity of the epidemic process, and (3) verify the factors presented in the literature that favor infection. The study showed that the situation of individual cities in terms of the course and intensity of the epidemic is not influenced by their size or functions, nor by their location within the country. Also, the influence on the level of infections of such features, often mentioned in the literature, as population density, poverty level, percentage of post-working age population or the level of healthiness of the population, was not confirmed.
The COVID-19 pandemic, of which cities are considered epicenters, caused the greatest social, economic and financial shock of the 21st century. The reconstruction of the process of the pandemic's spread in cities, the identification of factors contributing to and preventing infection with the SARS-COV-2 virus, and the search for ways to combat it and its consequences have become the subject of much research and analysis.
The results of the analyses presented in the article "SARS-COV-2. "Cities in the epidemic, the epidemic in cities: Reconstruction of COVID-19 development in Polish cities," published in the journal Cities. In it, the study included 20 large Polish cities with different functions, in a set of which: (1) the course of the infection process and its variation over time were determined, (2) cities were classified according to the similarity of the epidemic process, and (3) the factors promoting infection presented in the literature were verified (in this case, the research was also conducted on a set of 66 large cities).
In general, the relative number of infections (per 10,000 residents), i.e. the intensity of infection, determined on the basis of positive results of the tests conducted on COVID-19, was taken as the basis for the analyses, since only such data in Poland can be obtained for territorial units in the time series. However, it should be noted that any research that is carried out in the field of determining the course and intensity of the epidemic is, unfortunately, only indicative. This is a consequence of the lack of reliable, factually, temporally and spatially differentiated numerical data, which will probably never be obtained.
Studies have shown that the situation of individual cities in terms of the course and intensity of the epidemic is not influenced by their size, function or location within the country. Unfortunately, it has not been possible to identify factors that can affect infections, or at least determine the risk of infection. Thus, the influence on the level of infections of such characteristics, presented in the foreign literature, as population density, poverty level, percentage of post-working age people or the level of healthiness of the population, was not confirmed.
Thus, the results obtained demonstrate the individual nature of the development of the epidemic in each city and to the probable influence on the level of infections, other than the explanatory characteristics taken into account in the study, or to the level of infections as an effect of the synergistic influence of not only socio-economic characteristics. The solution to this issue remains an open question, as it seems, not only for Polish cities.
However, there is no doubt that it is necessary to make the cities of the future better prepared to respond quickly to epidemics, but how this preparedness is to be shaped remains an open question.