Abstract： Most of the world's population has been infected with SARS-CoV-2.Surveillance and epidemiological studies of SARS-CoV-2 infection,based on influenza-like illness,often underestimate infection rates because asymptomatic individuals seldom seek medical attention.Nucleic acid and antigen tests are used to identify early infections but may miss some infected individuals due to sensitivity limitations.Serological assays are frequently used to identify SARS-CoV-2 infections and reinfections in epidemiological research,but none have become standardized criteria for infection and reinfection.In this article,we summarize methods that are commonly used to identify SARS-CoV-2 infection and reinfection in real-world research to provide evidence for relevant study design and conduct.