COVID-19 is rapidly spreading. Patients in incubation period and healthy carriers are possible sources for transmission. However, such sources of infection cannot be effectively identified due to the symptoms absent. The research evidence is very lacking so far, although there are a few studies suggesting that presymptomatic or asymptomatic carrier may cause COVID-19 transmission. Nearly half of the literature is in the state of preprint without peer review. The question of "the degree to which presymptomatic or asymptomatic infections can transmit" is not fully understood. There is an urgent need to screen infected carriers in larger close contacts or in the general population, and assess their risk for transmission.
新型冠状病毒肺炎正快速向人群传播，潜伏期患者和隐性感染者都有向体外排出病毒而成为传染源的可能，但是由于临床症状隐匿，这类传染源无法有效识别，容易形成防控措施的漏洞。目前有研究提示该病潜伏期患者或隐性感染者可能造成疾病传播，但是研究仍然十分有限，而且近一半文献尚处于未经同行评审的预印本状态。对于"感染者能否在潜伏期传播病毒、无症状感染者是否可以传播病毒、效率如何"，尚无明确且公认的回答。亟待在更大的密切接触者或者一般人群中筛选感染者，并且评估他们传播疾病的风险。.
Keywords: Asymptomatic transmission; COVID-19; Presymptomatic transmission; Source of infection.