An elderly Chinese woman who was diagnosed with COVID-19 in February but recovered fully has tested positive for the disease again six months after, posing new challenge to the medical fraternity.

Apart from the 68-year-old woman from China's Hubei province, who tested positive again after developing symptoms on August 9, another man, found to have contracted the COVID-19 in April after returning from abroad, tested positive in Shanghai on Monday, August 10 though he did not develop any symptoms. Local Chinese authorities said none of the patients' close contacts has tested positive for the novel Coronavirus but they have been placed under quarantine.

The novel Coronavirus has infected more than 20 million worldwide and killed over 749,000 individuals globally. The resurgence of the virus in already recovered patients is rare, but these recent cases have triggered concern over the virus's ability to linger and appear in previously infected people.

Coronavirus Infection

Coronavirus
Coronavirus reinfection (representational picture) Xinhua/IANS

An Israeli doctor at Sheba Medical Center was tested positive for COVID-19, three months after she recovered from the virus infection. In the U.S., a Massachusetts man, aged 82, who spent almost four weeks in the intensive care unit at Massachusetts General Hospital after contracting the Coronavirus was once again struck down by the virus, that too in just 10 days.

All these Coronavirus cases are the latest in a series of incidents of suspected reinfection that has raised questions concerning how long immunity against the SARS-CoV-2 lasts. The resurgence of the virus in already recovered patients has also raised questions over why some COVID-19 patients suffer from long-term symptoms.

Cases of Reinfection

Coronavirus
SARS-CoV-2 Wikimedia Commons

As reported by Bloomberg, some healthcare experts have pointed out the possibility that other cells continued to provide immunity even after antibodies disappear. South Korean researchers earlier claimed that SARS-CoV-2 found in patients months after recovery from the disease could be the vestiges of dead virus particles that are no longer infectious.

An American physician, Clay Ackerly said that he had seen one of his patients who tested positive again for the virus, three months after recovery. As per the expert, while the first time the patient exhibted minor symptoms like cough and sore throat, the second time the person had severe symptoms, including high fever, shortness of breath, and dangerously low oxygen levels.

As per a report, Ackerly wrote, "Despite scientific hopes for either antibody-mediated or cellular immunity, the severity of my patient's second bout with COVID-19 suggests that such responses may not be as robust as we hope." He also added that "many people could catch COVID-19 more than once and with unpredictable severity."