Family cluster study of asymptomatic transmission: A 20 year-old woman from Wuhan, China (Patient 1) traveled to Anyang on January 10, 2020 and met with Patient 2 and Patient 3. On January 13, she visited a hospitalized relative with Patients 2-6. At this time, there were no reported cases of COVID-19 at the Anyang District Hospital. Patient 1 was isolated and tested/monitored for the following symptoms: temperature/fever, gastrointestinal symptoms, respiratory symptoms (cough/sore throat), chest CT, C-reactive protein, lymphocyte count. RT-PCR testing was negative on January 26, positive on January 28, and negative on February 5/8. Patients 2-6 developed COVID-19.