  Relevance: Laboratory diagnosis of the novel coronavirus (SARS-CoV-2)
infection combined with quarantine for contacts of infected individuals affects
the spread of SARS-CoV-2 infection and levels of related mortality. Practices
for testing for SARS-CoV-2 infection vary geographically in Russia. For
example, in the city of St. Petersburg, where mortality rate for COVID-19 is
the highest in the Russian Federation on Oct. 25, 2020, every death for
COVID-19 corresponds to 15.7 detected cases of COVID-19 in the population,
while the corresponding number for the whole of Russia is 58.1, suggesting
limited detection of mild/moderate cases of COVID-19 in St. Petersburg.
Methods: More active testing for SARS-CoV-2 results in lower case-fatality
ratio (i.e. the proportion of detected COVID-19 cases among all cases of
SARS-CoV-2 infection in the population). We used data on COVID-19 cases and
deaths to examine the correlation between case-fatality ratios and rates of
mortality for COVID-19 in different regions of the Russian Federation. Results:
The correlation between case-fatality ratios and rates of mortality for
COVID-19 in different regions of the Russian Federation on Oct. 25, 2020 is
0.64 (0.50,0.75). For several regions of the Russian Federation, detectability
of SARS-CoV-2 infection is relatively low, while rates of mortality for
COVID-19 are relatively high. Conclusions: Detectability of the SARS-CoV-2
infection is one of the factors that affects the levels of mortality from
COVID-19. To increase detectability, one ought to test all individuals with
respiratory symptoms seeking medical care for SARS-CoV-2 infection, and to
undertake additional measures to increase the volume of testing for SARS-CoV-2.
Such measures, in combination with quarantine for infected cases and their
close contacts help to mitigate the spread of the SARS-CoV-2 infection and
diminish the related mortality.
