The rapid spread of COVID-19 epidemic has aroused great concern worldwide. The COVID-19 is a kind of microbial pathogen, so cutting off the transmission path of the pathogen is the top priority for epidemic prevention and control. The most important link is to identify and detect the pathogen. So how is the pathogen detected? How many methods and categories are there? Which can serve as the diagnostic criteria? Now let's find the answers from Li Wei, a researcher of the Institute of Zoology, Chinese Academy of Sciences.