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COVID-19: Higher viral load in asymptomatic patients

In a study of over 200 patients with SARS-CoV-2 virus, carried out in Telangana, revealed that there is a greater association between higher viral load and asymptomatic COVID-19 patients. Viral load is the amount of virus present in the bodily fluid of an infected person.

The scientists, including those from the CDFD, Hyderabad, suggested screening of asymptomatic primary and secondary contacts of the COVID-19 patients.

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Murali Dharan Bashyam, CDFD’s Laboratory of Molecular Oncology said that it is necessary to study the probability of infection from asymptomatic patients – probably harboring good immunity – spreading into people having not so strong immunity resulting in higher morbidity and fatality.

Satyajit Rath, an immunologist, National Institute of Immunology, New Delhi said that the results of the research study showing greater viral loads in asymptomatic people really shocked him.

Satyajit Rath told that various other researches, as the researchers note, report an association the other way.

The foremost aim of the study is to recognize the dominant viral lineage circulating among the people of Telangana, specifically in Hyderabad. The outcomes of the study is released in the BiorXiv preprint repository.

The total number of cases in Telangana to 1.27 lakhs till date, the state has actually seen an unusually high rate of COVID-19 positive cases with a sharp spike observed in the number of cases from the second half of April.

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The highly frequent mutations in the viral genome were determined after the researchers analyzed whole-genome sequence data of virus samples from 210 patients in and around Hyderabad.

Bashyam said that the researchers discovered that most of the population under study (more than 95%) was infected with a 20B strain of SARS-CoV-2, while a few samples belonged to other strain and substrain.

Bashyam added that more notably, 100% of the virus from the period of May to July comes under the 20B strain.

According to the researchers, the first entry of the infection in Telangana came from 2-3 different viral strains, and the 20B strain had the ability to entrench itself as the majority strain.

Additionally, a high predominance of D614G spike protein mutation, which currently has been related to greater infection rates, was also observed in the study.

A couple of distinct mutations in a functionally critical region of the non-structural protein 3 (nsp3) of the virus, responsible for duplication of the viral genome – most notably- not identified from other research studies in India, was also identified in this study.

Contrasted to samples collected before May, the samples collected from late May till July noted a greater percentage of asymptomatic cases, as per the researchers.

According to the researchers, most of the samples were of the age group 15-62 years, with males (61%) and females (39%).

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The researchers contrasted the distribution of cases with regard to cycle threshold values (is the number of cycles needed for the fluorescent signal to cross the threshold or surpass the background level), which is a proxy for viral load.

The research discovered that compared to asymptomatic cases, symptomatic cases seemed to be related to greater cycle threshold values, thus reduced viral loads.

In an RT-PCR test, a positive reaction is identified by the buildup of a fluorescent signal.

The samples examine near the end of June showed a decrease in the cycle threshold values, suggesting that more recent samples seemed to carry a higher viral load than initial samples.

Bashyam added that they have observed a reasonably higher association between viral load and asymptomatic patients. But, this association is substantially based on numerous aspects including the general immune health during sample collection and the sample demography.

He added that this data refers to samples until the first week of July, and it would be interesting to investigate whether the trend proceeded until now.

Bashyam said that the spread of the virus is based on numerous aspects, however, based on the outcomes of the study, it is currently vital to start research on the possible transmission of the virus from asymptomatic people.

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He stated that one more fascinating findings of the research were that many samples came from the age group of 20-50 years, and one would certainly anticipate that increased immunity would be present in this age group.

All the scientists and clinicians worldwide are studying constantly as well as recommending corresponding governments based on which they can take enlightened public health choices.

Bashyam stated that it is necessary to proceed to work similarly to the one they have done to ensure that the state government can be much better educated regarding the viral spread.

He added that they will surely recommend screening asymptomatic primary as well as secondary contacts.

The researchers stated that it is hard to theorize the outcomes of the study to other Indian states, due to the large range of genetic heterogeneity in the Indian populace.


Author: Sruthi S