| Summary: | The outbreak of Coronavirus disease 2019 (COVID-19) firstly appeared in China on December 1, 2019 and led to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly spread to many other countries. The World Health Organization (WHO) declared it as a pandemic on March 11, 2020. The pandemic affected 2,719,897 people in the World and 187,515 people died until April 25, 2020. In the early period, many developed countries considered the COVID-19 outbreak as a simple flu epidemic. By implementing the herd immune strategy, they aimed to gain immunity by allowing a certain number of people to have mild illness and to easily control the outbreak within a few months. However, the virus spreads faster than its ancestors such as the SARS-CoV and the Middle East respiratory syndrome coronavirus (MERS-CoV) with an estimated death rate of 2 to 3%
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