Large differences in the number of registered SARS-CoV-2 cases per capita in different countries encourage research into the causes of this phenomenon. In particular, a strong linear correlation was revealed between the gross domestic product per capita (GDP) and the numbers of cases per capita (CC) registered in African countries as of February 1, 2022. A non-linear correlation and datasets for African and European countries corresponding to August 1, 2022 show that CC values increase for richer countries probably be due to higher levels of testing. The much lower values of registered accumulated numbers of cases and deaths per capita (DC) in Africa are most clearly explained by the low testing level than by the influence of other factors. In some countries, the number of undetected COVID-19 cases may be tens or even hundreds of times higher than the number of registered ones, which increases the probability of the appearance of new dangerous SARS-CoV-2 strains and reduces the prospects for a quick end to the pandemic. Many unreported cases make it difficult to analyze the impact of vaccinations and other factors. In particular, the decline of DC values and the case fatality risk (DC/CC) with increasing vaccination rates in Europe requires additional research.