By Ashish Srivastava

New Delhi, Aug 21 (IANS): New aspects of the Coronavirus infection are coming to the fore as the pandemic continues its vice-like grip.

New symptoms are being discovered and so are residual symptoms. Complications and threats involved with catching the infection are also evolving. The latest issue being witnessed and discussed is the Covid-19 re-infection.

In the last few weeks, as many as five cases have emerged from Delhi alone. This month, the Delhi government-run Rajiv Gandhi Super Speciality Hospital reported two instances of patients with a relapse of Covid-19 after recovering one-and-a-half months ago.

Aakash Healthcare in Dwarka reported a case in July where a cancer patient re-contracted Covid-19 and died weeks after recovery. A Delhi policeman and a nurse in an MCD-run hospital recontracted the disease after recovery in July.

While the reports of re-infection are emerging, experts are questioning the legitimacy of reporting re-infection at the current stage of the disease spread. IANS spoke to some experts to get to the bottom of the matter.

Does retesting positive in RT-PCR mean reinfection?

As per the experts, the virus SARS-CoV-2 that causes Covid-19, lives in the body of the infected person even after the person recovers from the disease. However, the infection reduces to a point where the person becomes non-infectious.

Praveen Gupta, the Director, and Head of Neurology Department at Fortis Memorial Research Institute, Gurugram, said that the virus can be found in the stool of a recovered person for upto 30 days and more than two months in throat swabs from the day the symptoms start showing.

Mahesh Langa, an expert in Infectious disease at Columbia Asia Hospital, Pune, said that patients who recover can test positive in the RT-PCR test for as long as three months from recovery. It happens because the virus is not entirely eradicated from the body during recovery.

"Even if the patient has recovered, the residual of the virus sustains in the body and could show PCR positivity (a term used for cases detected positive via RT-PCR tests) for three months," he added.

"The virus gets isolated in the throat of the patient. So when a swab from the throat is taken for the test in RT-PCR, the result comes positive. But it doesn't mean that it is a re-infection," Dr Langa explained.

"One can test positive even after the full treatment of Covid-19. The virus sustains in the body even after recovery, but its strain becomes weak. However, the RT-PCR is a sensitive testing method, so the residual of the virus gets picked by the test, and the result comes positive," said doctor Col Vijay Dutta, a consultant in Internal and Respiratory Medicine at Institute of Spiral Injuries Centre, New Delhi.

Techniques to ascertain infectivity of virus

Dutta also concurred with Langa that showing positivity in RT-PCR does not mean re-infection. When asked how can it be concluded that despite the presence of the virus in the body it does not mean re-infection, they said that while the virus sustains in the body, it starts losing its potency after ten days and becomes non-infectious after 17 days of the onset of symptoms.

However, the doctors use two techniques to determine the virus' infectivity: viral culture and calculating cycle threshold (CT) value of the virus.

Viral culture is a laboratory technique in which samples of a virus are placed to different cell lines, which the virus being tested for is able to infect. "If the viral culture is negative, the virus has turned impotent despite showing positive results in the RT-PCR test," Langa said.

CT value basically provides information on the viral load in the disease. It is done during the RT-PCR test to check the amount of the viral RNA in the sample taken for the analysis and determine the potential infectivity of the virus.

"If it is calculated 40 or beyond, it is considered that the virus has turned non-infectious. The CT value of the virus in the patient suffering from Covid-19 is found between 10-27," informed Gupta.

Does re-testing positive with symptoms of Covid ensure confirmed relapse?

While the experts refute the possibility of re-infection, there are cases where the recovered patients are coming with the exact symptoms of Covid-19. When asked if such cases could be instances of Covid relapse, the experts said unlikely.

"There is a difference between showing symptoms again and the capability of contracting the virus. Patients of Chikungunya and influenza also suffer from the post-viral syndrome. The Herpes virus could also live in the body for a long time after recovery. Besides, the symptoms of Covid-19 are similar to many illnesses. Merely symptoms cannot determine that the re-infection has occurred," Dr Gupta.

Dutta also said that those who got infected earlier are now coming with complications secondary to either body-aches or lung infection, but it can't be called relapse. "It's not proven yet," he claimed.

The latest study by the Centre for Disease Control (CDC) of the USA also supported the claim by the experts. As per the study, the concentrations of RNA virus (Covid-19) measured in upper respiratory specimens decline after the onset of symptoms but could sustain for months.

The study found that the amount of live virus in the nose and throat drops significantly soon after Covid-19 symptoms develop. Additionally, the duration of infection in most people with Covid-19 is no longer than 10 days after symptoms begin and no longer than 20 days in people with severe illness.

It also estimated that 88 per cent and 95 per cent of their specimens no longer yielded replication-competent virus after 10 and 15 days, respectively, following symptom onset. It means the virus lost its infectiousness by 88 per cent after 10 days and 95 per cent after 15 days of a person developing symptoms.