The case of a Delhi policeman having a relapse of the novel coronavirus has baffled experts and the doctors treating him and has raised the question whether a recovered patient can contract the infection again.
The policeman, 50, had tested positive for the virus in May and was treated at the Indraprastha Apollo hospitals between May 15 and 22. Thereafter, he had tested negative and resumed duty.
However, on July 10, he again felt unwell with a fever and dry cough and got himself tested on July 13.
The report came positive through the rapid antigen test as well as the RT-PCR test, said Dr Rajesh Chawla, Senior Consultant, Respiratory and Critical Care Medicine, Apollo Hospitals.
The policeman, who has no other underlying ailment, complained of chest pain on July 16 and was admitted to the hospital, the senior doctor said, adding that he is stable and his vitals are being monitored.
"The first time he was tested for coronavirus, he had no symptoms. There was a camp in the hospital and since his friend got tested, he also got tested and came positive,” he told PTI.
The second time the policeman was tested for antibodies too, but it was found that he did not have antibodies, he said.
What could be the reasons for the relapse of infection?
"If it was within a month,” said Dr Chawla, “I would have said that it was a dead virus that was giving a positive result. But that is not the case.”
“The other thing could be that it was a false positive when he was tested the first time, although it is very rare in RT-PCR test but still it can occur. The third, of course, is reinfection because he did not have antibodies. I have not seen any other such patient," he said.
Dr Mugdha Tapdiya, Senior Consultant, Internal Medicine, Fortis Hospital, Vasant Kunj, concurred with Dr Chawla.
It is possible that a right level of antibodies was not developed against the virus which meant that when the patient was exposed again, he got reinfected, she said.
She also did not rule out the possibility that the first result was a false positive.
Earlier this week, a similar case had surfaced in the national capital after a nurse employed at a civic-run dedicated COVID-19 hospital had tested positive again after recovering.
However, the municipal authorities had claimed there was nothing to worry as it is ostensibly the “dead virus” left in her body from the previous infection.
The officials had said that her IgG antibody level is “very high, which also corroborates this explanation".
Explaining the recurrence of the infection, Krishnan Harshan, a virologist with the Centre for Cellular and Molecular Biology, said these could be "sporadic cases".
"There are two aspects to it. If the virus is found again in recovered patients, there is either some problem with the test or there is some issue with the immunity of the people who have been re-infected," he told PTI.
The immunity against the virus also stays in the body for sometime, he said, adding that unlike the HIV, which is a latent virus and integrates with the genome of the host, the coronavirus doesn't show anything like that.
Dr Tapdiya it has been a matter of study all over the world.
"There have been a few places like Korea, China where there was recurrence or relapse of infection. Actually there are two sets of patients where it has been seen -- first the disease was mild, and in the second episode, it became severe. In the second set of patients, the disease was moderate or severe in the first instance and then in the second instance also, it was severe.
"But at no point in both the cases it was proven that in the first case when the patient was asymptomatic it was a false positive and when he came positive the second time, it was a true positive," she said.
The senior doctor also said that recovered patients lower their guard and they become a little bold thinking they won't contract the infection again after catching it once.
"It has also been seen that people who have had a milder infection or are asymptomatic, do not have enough immunity, which is also a theory proposed.
"It is very important that for every mild and asymptomatic test beyond the 14th day, we should get an antibody test done for testing their immunity. At no point, they should lower the guard," Tapdiya added.
“As of now, you are at an equal risk of contracting the infection again.”