A virus, such as the Sars-Cov2 virus causing the Covid-19 pandemic, typically consists of a genome in a protein coat and can multiply only within the living cells of a host. The genome can either be composed of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The nucleic acids can undergo a dynamic change in their chemical nature through a process called mutation, which can be triggered by the physiological environment a virus invades or by mutagenic factors in the host.
Having a genome made of RNA, in particular, has two significant caveats. First, by its very chemical composition RNA is unstable and more susceptible to mutations. Second, viruses with an RNA genome do not have the biological capability to correct such mutations unlike viruses with a DNA genome. The Sars-Cov2 is an RNA virus and such viruses usually undergo much faster genomic changes once they enter their host. A typical RNA virus can, on an average, undergo more than half-a-dozen mutations in each human-being it infects. And that, precisely, is the danger.
The biological character of a microbe is defined by its genomic composition, thus the pathogenic behaviour of such viruses — especially their virulence and infectivity — may drastically change with mutations. This also helps such viruses evolve at a rapid rate. This is exactly what has been observed with the Sars-Cov2 virus — it was seen to evolve into two different genetic strains apparently within two months, now defined as its “S” and “L” type. Several scientists claim that the L type is more aggressively virulent than the S type. However, this information came from the genome analysis of just 103 Chinese patients at the end of January this year. Now, two-and-a-half months after the study, the virus looks more virulent than originally predicted, having infected more than 1.7 crore and has killed over a lakh worldwide. Thus, it is time we reassessed whether it has assumed a more lethal genetic trait.
Also, mutations in the viral genome can change the composition of their coat proteins against which vaccines are designed, making such vaccines ineffective. While scientists have already come up with prospective vaccines against this virus, it would take several months for them to pass the required efficacy tests and mandatory human trials to qualify for use. Can we afford to wait given the alarming rate at which the virus is invading us and the uncertainty about the vaccines’ final efficacy?
Moreover, the kits we use to detect the Sars-Cov2 involve signature genetic motifs. Mutational changes may therefore pose a serious challenge to the confirmatory nature of such tests. Therefore, we desperately need to know the present genetic character of this virus in our country as well as the precise number of genetic strains pervading our population — because we have carried this virus into India from diverse countries during different stages of this pandemic.
The international database for the Sars-Cov2 genome reveals that very few among the 200-plus affected countries have given the study of its dynamic character the importance it deserves, barring China, Japan, the US and Italy. It is heartening to see that our neighbour, Nepal, has put in the effort to sequence this genome. Of the 150-odd full genome sequences released globally, India is responsible for two. The first such sequencing, by the National Institute of Virology in Pune, was of the virus derived from the first three Covid-19 patients who returned from Wuhan at the end of February. This genome, naturally, matched the sequence released by China. The second genome sequence, however, aligned with the one released by the US. This indicates the presence of at least two different strains in our country — perhaps more, considering that the virus entered this country through multiple human carriers from different demographies till the end of March.
What is baffling is that although India has sufficient scientific resources and manpower to support exercises needed to manage the Covid-19 crisis — including research for kit development, genome sequencing and testing — it has, perhaps as a policy, only utilised institutes affiliated to the Indian Council of Medical Research (ICMR) to tackle this insurmountable task. In fact, only one institute, the Indian Institute of Virology in Pune, held access to the Sars-Cov2 virus for research purposes while some ICMR institutes deployed only a single scientist to handle the validation of testing kits being manufactured in the country, causing unnecessary delay.
Recently, the Government of India’s Empowered Committee for Covid-19 has approved all national laboratories with required resources to participate in the testing and culturing of the Sars-Cov2 virus for research purposes. This should allow equipped labs to take up necessary research, including extensive sequence analysis of the Sars-Cov2 viral genome. However, we need to do this fast to ensure that the virus doesn’t outpace us like it has in some of the most advanced countries of the world.
Although it is difficult to assess the precise status of the Covid-19 outbreak in our country because of inadequate community testing, we should be able to control this pandemic by rapidly scaling up our testing capability. We should also make an accurate assessment of the exact genetic nature of the Sars-Cov2 strains present in India. This will help us not only to devise effective detection and therapeutic strategies but also to have a clear understanding of the transmission path concerning “who infected whom” to facilitate contact tracing. This can indeed be a decisive factor in determining our final fate against this perilous virus.
The writer is head of the department of biotechnology in the University of Calcutta
