Factors affecting mortality for the novel coronavirus infection in different regions of the Russian Federation

Background. The influence of such factors as population density, practices for testing for the SARS-CoV-2 (combined with quarantine/self-isolation for infected individuals and their contacts) and ambient temperature on the spread of the novel coronavirus infection and related mortality in the 85 different regions of the Russian Federation isn’t well characterized.Materials and methods. Population density in the different regions of the Russian Federation is measured as the number of persons per square kilometer of settled areas; ambient temperature is measured as the mean for January and July values; practices for testing for SARS-CoV-2 are characterized via case-fatality rates (the percent of deaths among cases with known outcome (recovered + fatal)) — under more active testing for SARSCoV-2, greater numbers of mild/moderate cases of infection are detected, resulting in the decline in case-fatality rates, i.e. the intensity of testing is inversely proportional to the case-fatality rate.Results. The correlation between population density and rates of mortality for COVID-19 per 100,000 persons on November 22, 2020 in the 85 different regions of the Russian Federation is 0.53 (0.36; 0.67); the correlation between case-fatality rates and rates of mortality for COVID-19 per 100,000 persons on Nov. 22, 2020 in the different regions of the Russian Federation is 0.62 (0.47; 0.74). Results of the linear regression suggest a positive association between population density, as well as case-fatality rates and rates of mortality for COVID-19 in the different regions of Russia, and a negative association between ambient temperature and rates of mortality for the novel coronavirus infection.Conclusions. Lower population density, more active testing for SARS-CoV-2 and higher ambient temperature are associated with lower rates of mortality for COVID-19. In particular, additional measures should be implemented towards testing of different categories of individuals for SARS-CoV-2, including those seeking testing on their own initiative, those seeking medical help with respiratory symptoms, and contacts of confirmed COVID-19 cases