The first group included the following index patients: Patient #3 was a 54-year-old man who was asymptomatic upon arrival in Korea on January 20th, but had developed a fever, chills, muscle ache, and nasal congestion by 13:00 on January 22nd. Patient #28, who was on the same flight bound from Wuhan to Korea as Patient #3, tested positive on February 10th during self-quarantine. The route of transmission is still under investigation. In addition, since Patient #28 underwent surgery following entry into the country, and was treated with antibiotics and analgesics, the exact date of onset of symptoms could not be calculated. Patient #6, an acquaintance of Patient #3, dined at a restaurant with Patient #3 on the evening of January 22nd for an hour and a half, developed symptoms including the chills on January 26th, and tested positive for COVID-19 on January 30th. Patients #10 and #11, the wife and son of Patient #6 who lived and dined at the restaurant with him, developed symptoms on January 29th and 30th, respectively, and tested positive for COVID-19. Patient #21, an acquaintance of Patient #6 who attended on January 26th, developed symptoms on January 30th and subsequently tested positive for COVID-19.