In this work, we discovered a new phenomenon-asymptomatic COVID-19 infection, or covert case, during the pandemic . All the 3 patients had a history of exposure, with no symptoms, and no abnormalities were found in computed tomography scan or lab tests . Except for case 2, the other patients' severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) nucleic acid tests were negative . But their anti-SARS-COV-2 nucleocapsid antibody showed a dynamic trend, consistent with the process of virus infection and clearance . A growing number of asymptomatic or covert cases need more attention . Lack of surveillance may lead to another outbreak . We hope to demonstrate our cases to attract the attention of governments or health authorities that covert cases should be the focus as well.