SARS-CoV-2 is the virus behind the 2019 Coronavirus Disease (COVID-19) and was first reported in Wuhan, China in December 2019. Since then, SARS-CoV-2 has continued to spread to surrounding 192 countries and regions. As of June 19, 2021, more than 177 million people have been infected worldwide. The United States reported its first SARS-CoV-2 case on January 21, 2020. The case was a 35-year-old American citizen who returned to his home in Washington State from Wuhan, China. The date of onset of symptoms for this person is January 19, 2020. Importantly, the other two of the 12 cases first detected in the United States around this time set the date of their symptoms on January 14, 2020. It was not until later in 2020 that researchers at the Centers for Disease Control and Prevention (CDC) discovered that people in several states in the United States were infected with SARS-CoV-2 earlier than in January 2020.
https://www.news-medical.net/news/20210621/Study-shows-that-COVID-19-was-present-in-five-states-in-December-2019-even-before-the-first-reported-case-in-China.aspx