Epidemiological patterns and features of SARS-CoV-2 on a regional, territorial scale and at the level of megacities

Abstract

The fight against a new coronavirus infection (SARS-CoV-2) has been ongoing for more than two years and has clearly been delayed, necessitating an epidemiological assessment of the status of the solution, successes and shortcomings in the control of the problem on both global and regional scales. An monitoring, epidemiological analysis of SARS-CoV-2 morbidity and mortality in WHO regions and selected territories by month and week for 2020–2021 and partly for 2022 was performed. It was found that the monthly trend of morbidity and mortality in their comparison across WHO regions and in individual countries repeats to some extent the weekly dynamics, but is not equal to it in the territories under comparison. It shows the wavelike epidemic process of the new coronavirus infection caused mainly by the emergence and circulation of new variants and subvariants of the pathogen among the population. An attempt was made to explain some features of the wavelike course of the epidemic process of COVID-19 depending on a number of other additional risk factors. Significant risk factors for the spread of the infection include a low level of social responsibility of the population not providing the necessary amount of measures (masking regime, non-compliance with social distance), uncontrolled travel regulation and, finally, a low level or complete absence of collective immunity to new mutation variants of the virus. Collective immunity formed as a result of disease transmissions and specific prophylaot pxis does protect completely against infection with new virus variants, but ensures a lighter course of the disease in cases of infection, reduced hospitalizations and deaths. Morbidity and mortality from COVID-19 in Russia, Moscow and St. Petersburg are also characterized by a wave-like course, however the indicators at the height of waves and in the intervals between them don’t decrease. The reason for this situation could be overdiagnosis, shortcomings in identifying the new variant of the virus. The delta variant, characterized by a more severe clinical course and unfavorable outcomes, is still circulating in some territories. Therefore, vaccination with coverage of 80 % of the population, including 60 % of the booster dose should ensure a decrease in the incidence and prevalence of all variants of the virus, the frequency of hospitalizations and deaths. Proceeding from the wave-like nature of the epidemic process in Russia and its metropolitan areas, all preventive measures should be strengthened not only at the peak of the epidemic, but also between waves in order to prevent infections and reduce morbidity and mortality. The need for measures is evidenced by the dynamics of increasing rates from the summer to the autumn-winter period of the year. However, analysis of weekly dynamics of morbidity should be taken as a basis for monitoring and accounting for changes in the epidemic process.