Doctors and clinical investigators involved in treating coronavirus infection have claimed that there was no evidence of the disease recurring in people who have recovered from it.

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However, Dr. Giridhar Babu, who is part of ICMR's research task force on Epidemiology and Surveillance, said it is difficult to say confidently where or not there is relapse in recovered patients as some signs post-recovery can be confused with COVID-19 symptoms.

One has to establish that the coronavirus has caused new infection in a recovered patient, he said. "We are up against evidence from all over the world where we are seeing there is no re-infection so when we say that is happening only in India then it maybe something new," Babu said. Dr. Swapnil Kulkarni, a chest specialist at the pulmonology department of Mumbai-based KEM Hospital, said there is no definitive evidence of re-infection in recovered patients. "There were reports from China earlier this year about recurrence of the infection, but no further information was received on that and other than that there were no reports of relapse," said Kulkarni, who has been treating COVID-19 patients in Pune.

There have been cases wherein results of RT-PCR test have come out positive for patients who have recovered as this test detects remnants of the dead virus in the body, Kulkarni said. Dead articles or remnants of the virus are harmless and take one or two months to get cleared from the body, Kulkarni said, adding that there is no clarity on whether these tests come out positive because of re-infection or due to presence of old remnants.

Apart from this, the percentage of false negatives and positives is quite high in RT-PCR tests, Kulkarni said. "Several recovered patients come for follow-up, but we have not come across any case of recurrence with proper symptoms," Kulkarni said. Babu, of the ICMR research task force, said, "In order to establish that the virus has infected a recovered patient again, we have to show it in the culture of the virus in the laboratory and it requires BSL 3 level lab facilities."

The phenomenon can be confused with post-COVID-19 symptoms such as weakness, breathlessness and poor oxygen saturation which may continue for some time in recovered patients, Babu said. Dr Sudhir Patsute, medical superintendent, Naidu Hospital, also denied any reports of relapse or recurrence of the infection. As on August 19, Maharashtra has recorded 6,28,642 COVID-19 cases and 21,033 deaths.