Abstract： Coronavirus disease 2019 (COVID-19) is an infectious disease caused by a novel Coronavirus, 2019-nCov. As of December 24th, 2022, the COVID-19 pandemic has spread to over 220 countries and regions, with a total of more than 770 million confirmed cases and 6.6 million deaths. The pandemic has had a profound impact on the global economy, political landscapes and daily life. The 2019-nCoV undergoes continues mutation, with variants exhibiting increased transmissibility triggering multiple waves of outbreaks worldwide. Once inside the human body, the 2019-nCoV replicates, and its viral load undergoes continuous fluctuations. The comprehension of virus clearance patterns can help epidemic prevention and control and disease diagnosis and treatment. This paper presents an overview of research advancements in the changes following infection with 2019-nCoV, from the perspectives of viral replication and immune clearance.