A higher positive rate indicates that a country has more undetected covid-19 carriers. Every country needs to increase their testing to minimize the positive rate. By increasing the covid-19 test to detect more undetected covid-19 carriers and isolate them to prevent them from infecting others, thereby reducing the number of undetected covid-19 carriers in the country. The new covid-19 mutants usually have a higher transmission rate, the maximum positive rate must be lower to ensure that the undetected virus covid-19 carriers are low and the country is controlled. Different countries may face high infection with different covid-19 mutants, Therefore, each country must have a specific maximum positive rate based on its country's covid-19 mutant. This book will provide a general formula to determine the maximum positivity rate for each country based on its country's covid-19 mutant. 3rd Edition update some information and add latest information on new covid-19 mutants.