The studies on infectiousness of person infected with SARS-CoV-2 at different stages of illness are an important basis for making effective prevention and control measures such as investigating the infectious source, determining the scope of close contacts and the timing of case isolation. This review discusses the infectiousness of cases infected with SARS-CoV-2 in the incubation period, symptomatic period and convalescent period by reviewing national and international literatures, technical and professional guidelines. Existing researches suggest that the infectious viruses could be isolated at the end of the incubation period as well as since illness onset, and viral load in upper respiratory tract swabs reached the peak on day 4-6 after illness onset and thereafter began to decline, implying the infectiousness was relatively strong at the end of incubation period and within one week after illness onset. Although there were a few cases who tested positive for SARS-CoV-2 after recovery, no evidence was found to indicate these cases can cause the transmission.
新型冠状病毒（新冠病毒）感染不同阶段的传染性特征是调查病例感染来源、确定密切接触者范围和病例隔离时间等防控措施的重要基础。本文通过对国内外文献、技术报告与专业指南等资料进行综述，基于病原学和流行病学两个维度的研究结果，探讨新冠病毒感染者在潜伏期、临床症状期和恢复期阶段的传染性特征。现有研究提示，新冠病毒感染者在潜伏期末和发病期均可分离到具有感染性的病毒，发病4～6 d后在上呼吸道样本中病毒载量达到高峰，随后开始下降，提示在潜伏期末和发病1周内的传染性相对较强。个别病例在恢复期尽管可再次检出新冠病毒核酸，但未发现具有传染性的证据。.