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In the fight against the pandemic of COVID-19, it is important to ascertain the status and trend of the infection spread quickly and accurately.

The purpose of our study is to formulate a new and simple indicator that represents the COVID-19 spread rate by using publicly available data.

The new indicator

The analysis of the current status of COVID-19 spreading over countries showed an approximate linear decrease in the time evolution of the

The approximate linear decrease of the

The spread of COVID-19 has resulted in human and economic losses worldwide. To prevent the spread of the infection, it is sometimes necessary to restrict social activities by policies such as the blockade of cities and the prohibition of assembly. For the effective implementation of these policies, it is important to ascertain the status and trend of spread quickly and accurately. The purpose of our study is to formulate a simple indicator that represents the COVID-19 spread rate by using publicly available data [

To analyze the trend of COVID-19 spread, we introduced a new indicator

The

Countries’ policies affected the transitions of the

In Asian countries, after the first wave originated from China, the subsequent spread worldwide caused the upward change in

Transition of the

As a new indicator of the COVID-19 spread rate, we have proposed the

We have found that the ^{t}^{t}

To test the long-term reliability and the validity of the assumption, we compared the model calculations with real data for Japan, France, Germany, and the United States. Using the

To understand the behavior of the

In the United States and Japan, several changes in the slope of the

The model parameters _{i}_{i}_{i}_{i}^{c}_{i}^{c}_{i}_{i}_{i}_{i}^{c}_{i}_{src} is found by minimizing the weighted mean squared deviation L(P) = ∑_{d}_{∈}_{D}^{2}/_{src}=4, and the resulting parameters are given by _{i}/dt

For the United States, the first peak position (March 26, 2020) clearly corresponded to the date of the change in the slope

The model results of the total number of infected people and the _{i}/dt

The analyses revealed that the time evolution of the

Novel indicator of change in COVID-19 spread status.

susceptible-infected

susceptible-infected-removed

We thank Prof Y Kaneda (Vice President of Osaka University), Prof T Yoshimori (Graduate School of Frontier Bioscience, Osaka University), Associate Prof Y Yasuda (Graduate School of Economics, Osaka University), Prof F Ohtake (Graduate School of Economics, Osaka University), and Mr S Shimasaki (Embassy of Japan in the United States) for helpful discussions.

None declared.