Fireflighters conduct disinfection to implement environmental health and epidemic prevention requirements at a farm produce market in Hubei Province, June 18, 2020.Photo:China News Service

A 68-year-old woman in Jingzhou, Central China's Hubei Province, tested positive for COVID-19, after she recovered and was discharged from a local hospital as early as February. 

A virologist said that the rare case shows it probably takes a long time to eliminate the coronavirus from the human body, but the scientist asserted that people who tested positive again after recovering from COVID-19 are not infectious.

The patient in Jingzhou tested positive again on August 9, who was discharged from hospital in February. 

She is put under quarantine for treatment, and all of her close contacts tested negative for the virus. 

The case indicates that it will take a long time to completely eliminate the virus from the human body, and the density of the virus inside this specific patient's body was low, which may explain why she had tested negative, Yang Zhanqiu, deputy director of the pathogen biology department at Wuhan University, told the Global Times. 

The virologist cited scientific studies to say that "re-positive" COVID-19 patients are not infectious.

South Korean researchers tested 790 people who had been in close contact with "re-positive" patients. Of the 27 patients who tested positive for the second time, none of them appeared to be caused from exposure to someone who was ill.

The report also found that 96 percent of recovered patients had neutralizing antibodies, indicating that they conferred immunity.