1 Estimation of Infection Rate and Prediction of Initial Infected Individuals of COVID-19 Seo Yoon Chae 1 , Kyoung-Eun Lee 2,3 , Hyun Min Lee 1 , Nam Jung 1 , Quang Ahn Le 1 , Biseko Juma Mafwele 1 , Tae Ho Lee 1 , Doo Hwan Kim 1 , and Jae Woo Lee 1,4,5 1 Department of Physics, Inha University, 100 Inharo Michuhol-gu, 22212 Republic of Korea 2 Ecology and Future Research Institute, 21 Dusilo, Geumjeong-gu, Busan, Korea 3 National Institute of Ecology, 1210 Geumgang-ro, Maseru-myeon, Seocheon-gun 33657, Korea 4 Institue of Natural Basic Sciences, Inha University, 100 Inharo Michuhol-gu, 22212 Republic of Korea 5 Institue of Advanced Computational Sciences, Inha University, 100 Inharo Michuhol-gu, 22212 Republic of Korea Abstract We consider the pandemic spreading of COVID-19 for some selected countries after the outbreak of the coronavirus in Wuhan City, China. We estimated the infection rate and the initial infecting individuals of COVID-19 by using the officially reported data at the early stage of the epidemic for the susceptible (S), infectable (I), quarantined (Q), and confirmed recovered (R k ) population model, so called SIQR k model. In the officially reported data we know the quarantined cases and the official reported recovered cases. We can’t know the recovered cases from the asymptomatic cases. In the SIQR k model we can estimated the parameters and the initial infecting cases (confirmed cases + asymptomatic cases) from data fits. We obtained the infection rate in the range  = 0.233~0.462 , the basic