Mumbai: Freak Covid-19 cases show need to study virus

Virus sequencing is important to understand if people are getting reinfected with the same or different variants of Covid-19

After the recent discovery of cases where recovered Covid-19 patients got mucormycosis and then tested positive for the virus, too, experts across segments have said that unusual cases must be documented and the sequencing of the virus must be done more frequently. These could provide more clarity on such cases and aid research.

Virus sequencing is important to understand if people are getting reinfected with the same or different strains of Covid-19. Representation pic

Professor of Global Health at the University of Washington-Seattle, Dr. Subhash Hira, who has extensive experience in managing mucormycosis in HIV/AIDS patients in Africa said while referring to a mid-day report, "A teaching hospital in Mumbai is investigating 26 mucormycosis cases that came during May-June. Of these five patients had undergone four to six weeks of treatment for Covid-19 and developed ‘black fungus' within one to five days of discharge. All five also tested positive for Covid-19, which has started a debate among doctors."

Possible ways of reinfection

"The main concern was that make-shift Covid-19 hospitals in Mumbai's suburbs could have been a source of black fungus for the five patients. The floating mould that grows on moist ground and wet walls needs to be investigated as the likely source, among others. With regard to them being Covid-19 positive, there are two possibilities - one that the negative test at the time of discharge was due to a low viral load. When these patients came in again with black fungus, they could be experiencing a recurrence of the first Covid-19 episode with a higher viral load. Second, it may be a re-infection that occurred within days of their discharge. These two possibilities can be differentiated by sequencing the two virus samples (if the first sample is preserved)," said Dr Hira.

Dr Shashank Joshi, consulting neurosurgeon

He added, "As they get investigated further, the cases will throw up many more solutions. An unknown facet that needs to be investigated is whether or not they took the vaccines."

Dr Prashant Kewle, ENT HOD ENT Anterior Skull base surgeon at Sushrut hospital Chembur, said, "There is a low possiblity that the first Covid-19 infection will recur after a negative RT-PCR test. But a person may contract a new infection with another strain of the virus. And RT-PCR test will be positive again."

Dr Wiqar Shaikh, Professor of Medicine at Grant Medical College and Sir JJ Group of Hospitals said getting infected once by Covid-19 does not guarantee lifelong immunity. This is irrespective of negative tests and subsequently getting black fungus. Dr. Shaikh said that corticosteroid injections such as dexamethasone given to Covid-19 patients, which are known to suppress the immune system, could be the primary reason for mucormycosis. "We have also seen people who took two doses of the Covid-19 vaccine and developed the infection and even got hospitalised," he said. The classic example, he added, was of former IMA President Dr KK Agarwal who took both doses and yet developed Covid-19, was hospitalised and died last month.

Dr Shaikh quoted a research paper published on June 14 in the journal ‘Nature', which concluded that immunity after Covid-19 may last up to 12 months and may be only slightly stronger after vaccination. "The only way for Covid-19 to stop infecting people repetitively is for the pandemic to go away completely, which does not seem to be happening soon. The other way out is for the entire population to develop ‘herd' immunity either the natural way or through vaccination of a large chunk of them," Dr Shaikh said.

Dr Shaikh added that cases of repeated Covid-19 in patients with mucormycosis become an extremely important subject for analytical study and research to know the underlying immunological reasons for such repeated infections and also to get the same documented and published for future referrals.

Recurring infections exceptional

"Recurrent infection from the same virus is not a rule but an exception as the human body forms virus-specific antibodies that make people resistant to recurrent infections," said Dr Shashank Joshi, consulting neurosurgeon. Dr Joshi, added, "This phenomenon has been widely used by medical scientists to prepare vaccines which are either inactivated viruses or their components. These vaccines are supposed to trigger antibody response. Booster doses are supposed to augment the response further. But we are seeing a recurring viral infection in the cases of Covid-19." "Most probably a minor change in genetic material or proteins of the virus is responsible for such a phenomenon. Frequent and mild changes in genetic sequence are called ‘drift', while major changes are called ‘shift'. Such pandemics occur as a result of shifts in genetic sequences. However, drifts will keep the virus and disease in active form for a few more years in the community," he concluded.