Global differences in changes in the numbers of population-adjusted daily test-positive cases (NPDP) and deaths (NPDD) by COVID-19 were analyzed for 49 countries. The changes per population of a hundred million were compared, adjusting by the beginning of test-positive cases increase (BPI) or deaths increase (BDI). Notable regional differences of more than 100 times in NPDP and NPDD were observed. The trajectories of NPDD after BDI increased exponentially within 20 days in most countries. A machine learning analysis suggested that NPDD on 30 days after BDI was the highest in Western countries (1180), followed by the Middle East (128), Latin America (97), and then Asia (7), and furthermore that, NPDD in Western countries with a positive rate of the PCR test of less than 7.0% attenuated to only 15%. The cause behind differences between regions might be complex, however, investigation of the host genetic factors would be warranted. The lower positive rate would be caused by aggressive testing policy and associated with longer lag times between BPI and BDI. Our analysis suggested that the positive rate need to be 7% or less by extensive tests to reduce deaths effectively. As the number of infected people is growing rapidly, earlier expansion of the test capacity is indispensable.

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Subject: Medicine and Pharmacology - Epidemiology and Infectious Diseases

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