Healthcare Development, Relaxed Natural Selection, and COVID-19 Infection Rates: An Evolutionary Population-Level Analysis

Background and Aim: Evolutionary principles offer critical insights into pandemic dynamics but have been largely overlooked in contemporary responses to COVID-19. Relaxed natural selection, increased global mobility, and lifestyle mismatches have contributed to human vulnerability to infectious diseases in modern societies. This study investigated the relationship between healthcare development, measured by the Biological State Index (I_bs), and cumulative COVID-19 infection rates across different countries and regions. Methods: Data from 189 countries were analysed to assess the association between the Biological State Index and COVID-19 infection rates, defined as the cumulative percentage of the population contracting COVID-19. Correlation analyses (Pearson's r and Spearman rho), partial correlations adjusting for aging, economic affluence, urbanization, and vaccination coverage, and multiple linear regressions were performed. Countries were further stratified by income level, development status, and WHO regions to explore group-specific patterns. Results: Higher Biological State Index values were strongly associated with higher COVID-19 infection rates globally (Pearson's r = 0.734, p < 0.001). Partial correlation analyses confirmed that this association remained significant after adjusting for key demographic and economic variables. Multiple regression models identified economic affluence and population aging as strong independent predictors, with the addition of the I_bs further improving model fit. Stratified analyses demonstrated consistently stronger correlations in developing and low- to middle-income countries compared to high-income and developed nations. Conclusions: Healthcare system advancement is strongly associated with higher reported COVID-19 infection rates, likely reflecting greater susceptibility, improved detection capabilities, demographic shifts, and broader exposure opportunities. These findings highlight the importance of integrating evolutionary perspectives into pandemic preparedness strategies, recognizing that modern healthcare developments, while reducing mortality, may inadvertently alter infection patterns and pathogen-host dynamics over time.