Viral Load Has Decreased In Current Covid-19 Samples, Says Dr Ajay Parida

Bhubaneswar: Not only have Covid-19 cases dipped in Odisha, but viral load in current cases of SARS-CoV-2 coronavirus infection has also decreased substantially than the earlier ones, informed Director of Institute of Life Sciences (ILS), Dr Ajay Parida.

“As per the latest findings, Ct (cycle threshold) value in RT-PCR test of Covid-19 swab samples which was earlier between 14-15 has gone up to 28,” said Dr Parida.

This indicates that the viral load has gone down, he added.

The ILS Director said, “In the last few days infection rate has decreased a lot. It has come to below 4000-5000 which is a very good sign. Testing has increased and if we compare it with that positivity rate is decreasing”.

He informed that Test Positivity Rate (TPR) is above 10% in seven districts which is the area of concern.

“Our prediction was that TPR will come down to below 5% in Odisha by June 15 which is what the trend shows. In districts where it is a little high it is likely to come down in a matter of few days,” Dr Parida stated.

He attributed the recent low number of cases to the good results of the lockdown imposed by the State government.

“Even if the government decides to relax the lockdown to some extent we have to remain on the alert, otherwise again we will be back to square one,” the ILS Director cautioned.

Among various scientific terms that have become public vocabulary during the ongoing Covid pandemic is ‘Ct Value’ in RT-PCR tests for determining whether a patient is positive for Covid-19.

Then what is this Ct Value?

Ct value is the short form for cycle threshold.  Ct is a value that emerges during RT-PCR tests for detection of the SARS-CoV-2 coronavirus.

According to the ICMR advisory, the Ct value of an RT-PCR reaction is the number of cycles at which fluorescence of the PCR product is detectable over and above the background signal. Therefore, the Ct value refers to the number of cycles after which the virus can be detected.

If a higher number of cycles is required, it implies that the virus went undetected when the number of cycles was lower. The lower the Ct value, the higher the viral load — because the virus has been spotted after fewer cycles.

In an RT-PCR test, RNA is extracted from the swab collected from the patient. It is then converted into DNA, which is then amplified. Amplification refers to the process of creating multiple copies of the genetic material — in this case, DNA. This improves the ability of the test to detect the presence of virus. Amplification takes place through a series of cycles — one copy becomes two, two becomes four, and so on — and it is after multiple cycles that a detectable amount of virus is produced.