Classification of the infection status of COVID-19 in 190 countries

We propose a simple method to determine the infection rate from the time dependence of the daily confirmed new cases, in which the logarithm of the rate is fitted by piece-wise quadratic functions. Exploiting this method, we analyze the time dependence of the outbreak of COVID-19 in 190 countries around the world and determine the status of the outbreak in each country by the dependence of the infection rate on the number of new cases. We show that the infection status of each country can be completely classified into nine different states and that the infection status of countries succeeded in controlling COVID-19 implies the importance of the quarantine and/or self-isolation measure. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement no external fund was used. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: N.A. All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes N.A.