GENEVA: The World Health Organization said on Saturday that it was looking into reports of some Covid-19 patients testing positive again after initially testing negative for the disease while being considered for discharge.South Korean officials on Friday reported 91 patients thought cleared of the new coronavirus had tested positive again. Jeong Eun-kyeong, director of the Korea Centers for Disease Control and Prevention, said the virus may have been “reactivated” rather than the patients being re-infected.WHO said: “We are aware of these reports of individuals who have tested negative for Covid-19 using PCR (polymerase chain reaction) testing and then after some days testing positive again... We are working to get more information on those individual cases.” According to WHO’s guidelines, a patient can be discharged from hospital after two consecutive negative results in a clinically recovered patient at least 24 hours apart.Based on current studies, there is a period of about two weeks between the onset of symptoms and clinical recovery of patients with mild COVID-19, WHO said.