Background: COVID-19 is an acute infectious respiratory disease caused by SARS-CoV-2. It has caused many deaths worldwide. Asymptomatic patients may be as infectious as symptomatic patients, but they are harder to identify. It is difficult for asymptomatic patients to realize that they have been infected and seek medical treatment in a timely manner, which poses challenges to virus prevention and control measures. Methods: This study reports 30 asymptomatic Chinese COVID-19 patients from the same road engineering company who worked in Sudan during the epidemic. Our team listed their symptoms after admission, various monitoring indicators and disease course to provide more information on asymptomatic COVID-19 patients. Results: 30 asymptomatic Chinese COVID-19 patients’ throat swab tests for SARS-CoV-2 were positive. Through further genetic testing, we found that these 30 Chinese individuals were infected with the European strain of SARS-CoV-2 circulating in Africa. In this study, the infection events occurred across three continents and suggested that the European strain could be brought to Asia via Africa by asymptomatic infected individuals and that the incubation and infection periods may be long; these points should be considered in epidemic prevention and epidemiological investigations. Fourteen days of quarantine may not be enough. After having negative results on at least 5 consecutive nucleic acid tests spanning 30 days, a patient may subsequently have a positive test result. Conclusions: We present our diagnosis and treatment process to provide useful reference information for colleagues during the COVID-19 pandemic.