Influences of seasonal and demographic factors on the COVID-19 pandemic dynamics
Keywords:COVID-19 pandemic, epidemic dynamics in Europe, epidemic dynamics in Ukraine, mathematical modeling of infectious diseases, statistical methods
INTRODUCTION: The number of COVID-19 cases per capita (accumulated (CC) and daily (DCC)) are important characteristics of the pandemic dynamics indicating the effectiveness of quarantine, testing, and vaccination. They also indicate the appearance of new waves (e.g., caused by new coronavirus strains) and may be the result of various demographic and seasonal factors.
OBJECTIVES: We investigate the influence of the volume and the density of population and the urbanisation level on the CC values accumulated in European countries and regions of Ukraine at the end of June 2021 and the impact of seasonal factors on the DCC values by comparing their dynamics in the spring and summer of 2020 and 2021 for northern and southern regions.
METHODS: The influence of demographic factors on CC values was investigated with the use of linear regression. Since DCC values are very random and demonstrate some weekly period, we have used the 7-days smoothing proposed before. The second year of the pandemic allows us to compare its dynamics in the spring and the summer of 2020 with the same period in 2021 and investigate the influence of seasonal factors. We have chosen some northern countries and regions: Ukraine, EU, the UK, USA and some countries located in the tropical zone and Southern Hemisphere: India, Brazil, South Africa and Argentina. The dynamics in these regions was compared with the global one.
RESULTS: The accumulated number of cases per capita CC does not depend on the demographic factors used for analysis, although it may differ by about 4 times for different regions of Ukraine and more than 9 times for different European countries. The number of COVID-19 per capita registered in Ukraine is comparable with the same characteristic in other European countries but much higher than in China, South Korea and Japan. Some seasonal similarities are visible for global dynamics, EU and South Africa. Before July 2020, the southern countries demonstrated exponential growth, but northern regions showed some stabilization trends.
CONCLUSION: The CC values in Europe do not show any visible dependence on the volume of population, its density and the urbanization level. More or less similar seasonal behaviour of DCC values are visible for global dynamics in July and August. Unfortunately, we cannot conclude where the quarantine restrictions were the most effective since the dynamics of the pandemic are influenced by many other factors not considered in this study, in particular, the emergence of new strains and the large number of unreported cases.
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