两名中国的COVID-19患者在康复数个月后检测结果呈阳性

中国湖北一名68岁的女性在去年12月首次检测感染新冠病毒，然而在她康复6个月后，她的冠状病毒检测再次呈阳性；另一名再次感染的男子则是在今年4月份从国外回来后，被发现感染了新冠病毒，这周一他在上海再次检测出阳性。当地政府表示，患者的密切接触者均未对病毒进行阳性检测，但他们已被置于隔离状态。

两名中国患者在康复后再次感染病毒的案例，引起了人们对该病毒在已感染过的人身上重新出现的担忧。虽然康复的病人很少会再次检测呈阳性，但这一现象引起了人们的疑问：为什么有一些病人会出现长期症状，以及对这种疾病的免疫力是否过于短暂而无法防止再次感染？一些研究表明，受感染者可能建立的保护性抗体水平在几个月后就会迅速下降，这可能使得他们很容易第二次感染同一病原体。但也有相反意见。一些专家提出，即使在抗体消退后，其他细胞仍有可能继续提供免疫力。韩国的研究人员则认为，患者康复数月后检测到的病毒可能是不再具有传染性的死亡病毒颗粒的残余。

A 68-year-old woman in the central Chinese province of Hubei, where the novel coronavirus first surfaced in December, tested positive on Sunday, six months after she was diagnosed with Covid-19 and recovered. Another man found to have contracted the disease in April after returning from abroad tested positive in Shanghai on Monday but hasn’t shown any symptoms. None of the patients’ close contacts has tested positive for the virus, but they have been placed under quarantine, local authorities said.

Two patients in China that recovered from Covid-19 months ago tested positive for the coronavirus again, raising concern of the virus’s ability to linger and reappear in people who it previously infected. While it is rare for recovered patients to test positive again, the phenomenon raises questions over why some patients suffer from long-term symptoms, and whether any immunity to the disease might be too ephemeral to protect against re-infection. Some studies have shown the level of protective antibodies an infected person may build up to fight the virus quickly drop after only a few months, possibly making them susceptible to the same pathogen a second time. However, there is little evidence so far that re-infection has been occurring in this pandemic. Some experts have raised the possibility that other cells continue to provide immunity even after antibodies fade. Researchers in South Korea have suggested that the virus detected in patients months after recovery could be the vestiges of dead virus particles that are no longer infectious.  source

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