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New variants: The evolution of a virus

27 Jan 2021

  • A new Covid variant discovered in SL: Why is it mutating? 

By Dr. Dilshan Anthony Fernando   Epidemiology Unit Chief Epidemiologist Dr. Sudath Samaraweera recently reported to local media that an individual who arrived from the UK was found to be positive with the new variant of Covid-19. Then on Wednesday (26), it was reported that a new variant of Covid-19 (B.1.258 lineage), which is different from other variants of the virus previously identified in Sri Lanka, was found in the island. The Department of Immunology and Molecular Medicine of the University of Sri Jayewardenepura said that this new variant of Covid-19 bears similarities to the variants of Covid-19 that has spread in European countries such as Denmark, Iceland, Switzerland, Germany, and the UK. Currently, as it stands, the Covid-19-infected number has surpassed 100 million globally with over 2.15 million deaths. In Sri Lanka, the number of infected persons is more than 60,000, with more than 290 deaths. Initially discovered in the Wuhan Province in China in November 2019, the virus has since caused considerable damage to humanity and has turned our lifestyles upside down and forced us to get used to a “new normal”. However, the worst may not be over yet as news comes in from around the globe about these different new strains of Covid-19.   Why do viruses evolve and what are the implications?   Covid-19 belongs to a family of viruses known as Coronaviridae, which gets its name from the crown-like appearances of these viruses caused by the spike proteins on the surface of the virus. Human coronaviruses belong to the order Nidovirales, the family Coronaviridae, and the subfamily Coronavirinae, according to scientific nomenclature. These viruses cause mild to severe respiratory symptoms. Coronaviruses are usually spherical in shape and are enveloped by an outer covering of spike glycol-protein projections, which give it the crown-like appearance, and is called the solar corona. Similar to humans, plants, and all other living organisms, viruses are subject to the evolutionary process of “natural selection”. Even though viruses on their own are not living organisms, they require a living host to replicate in. The host’s immune system employs various mechanisms to evade or fight the viruses, while the viruses evolve in certain ways to evade the immune mechanisms in fulfilling its objectives to replicate itself more and spread. In the evolutionary process of viruses, the characteristics that increase its virulence tend to be carried forward and characteristics that tend to diminish the virulence are lost. When humans develop immunity to a virus, they develop antibodies to that virus which usually attach to the outer surface of a virus and prevent it from entering the human cells. However, a virus which has mutated and has a slightly different structure to the pre-existing virus has an advantage in the fact that no antibodies have been developed to that particular structural anomaly which has been caused in the mutation. Many of the mutations in the viruses over time cause changes in structure of the outer surface of the virus   Viral mutation leading to new strains   Viruses have genetic material called RNA (ribonucleic acid) which is similar to DNA. When a virus infects a host cell, they attach to the cells and infiltrate them and make copies of their RNA in their efforts to replicate and spread. When viruses replicate in a host there are “copying errors” which cause mutations of the viruses in the structure of the virus, leading to differences in their behavior as well. The term “viral mutations” may strike fear among many. However, it is important to understand that many of these mutations are minute and do not necessarily cause increased virulence or transmissibility of the virus or cause more severe reactions in the patients. Some mutations actually may diminish the effects of the virus. Hearteningly, studies show that the Covid-19 viral mutation rate is slower compared to other RNA viruses similar to it. However, it should be understood that Covid-19 is a relatively new virus infecting humans, and scientists and doctors are still studying the full length and breadth of its behaviour.   Earlier coronavirus strains   Even at the earliest stages of detection in 2019, researchers believed that there was more than one strain of the virus. This theory about different strains of the new coronavirus came from a study in China. The researchers were studying the structure of coronaviruses in animals and human beings; samples from 103 humans were studied, and it appeared that the samples from humans were not identical to each other. On further studies, two different types of viruses were classified in the early stages, type “L” and “S”. These two variants only had very minute changes. It is believed that type “S” came first but type “L” was more common.   New strains of the virus   In analysing the Covid-19 virus, the initial virus which started spreading in Wuhan is not what’s predominantly spreading globally currently. In February 2020, the D614G mutation emerged in European clusters and emerged as a dominant form. Studies on this mutation showed that compared to the initial virus strain in Wuhan, the D614G form had an increased transmission rate but it did not cause a more severe illness nor did it affect the effectiveness of diagnostics and therapeutics. Two other mutations were identified in Europe, the “A222V” which spread across Spain and another strain coined “cluster 5” which was found in Denmark, associated with mink farmers. In December 2020, it was reported from the UK about a new variant of Covid-19 coined as SARS-CoV-2 VOC 202012/01 (Variant of Concern, year 2020, month 12, variant 1). This variant initially appeared in Southeast England, but how and where it originated is unclear. By the end of 2020 this variant was predominantly found across England through testing. This variant has since been reported in other countries, including one reported case in Srilanka. As of 30 December, the VOC-202012/01 variant has been reported in 31 other countries, territories, and areas in five of the six WHO regions. Researchers estimate that the transmissibility of this strain could be up to 70% more. In this mutation, the changes have been on the spike protein on the virus, which the Covid-19 vaccines target. However, the vaccines produce antibodies against many parts of the spike proteins on the surface of the virus, thus one mutation is unlikely to reduce the effectiveness of the vaccine. Other countries Such as South Africa and Nigeria have reported new strains of the virus, which are found to be more transmissible than the earlier viral strains, but, similar to the UK variant, these do not make the illness worse. Centres for Disease Control and Prevention (CDC) reports that the UK variant and the South African variant are not linked to one another.   What do we know about the new mutations?   Studies thus far show 17 important alterations in the Covid-19 virus, out of which N501Y alters the most important part of the spike protein, called the receptor-binding domain, which attaches to the host human cell and results in antibody production. Any changes in the receptor-binding domain tends to give an edge to the virus. Studies done by the University of Cambridge suggests that this mutation increases infectivity by twofold according to laboratory studies. The virus mutation potential increases with the increase in frequency of human and animal infections, thus stemming the infection of the virus is extremely important in limiting the number of new mutations occurring in Covid-19. Avoiding the introduction of the virus to animal populations also plays a key role in limiting mutations. Even though the new strains are not found to be increasing the severity of the disease, the increase in rate of transmission itself will result in increasing the number of cases, which will increase the burden on healthcare workers and use up more and more resources. The global research community in collaboration with the WHO is vigilantly monitoring for new strains of Covid-19. A virtual forum hosted by the WHO saw 1,750 experts from 124 countries collaborating to share knowledge and expertise on emerging Covid-19 variants and possible measures to expedite and expand countermeasures.    Can it evolve further?   The question arises whether the Covid-19 virus can further evolve. As explained before, as long as the virus keeps transmitting and replicating in host cells, the potential for further mutations remain, but thus far, the mutations have not caused any difference in how the coronavirus behaves. Studies show that new variants of Covid-19 surface almost every week, but the majority of them have no major changes and fizzle out after a while   Will the vaccine be effective against the new variants? The million-dollar question in the current context is whether the emerging Covid-19 vaccines will be effective against these new viral strains. Research done thus far suggests that vaccines will be effective. However, all the leading vaccines develop an immune response to the protein spike of the virus, the structure which has been mutating. Vaccines train the immune system to attack several different parts of the virus, so even though part of the spike has mutated, the vaccines should still work. However, further mutations may potentially lead down a path for “vaccine escape” which would mean the vaccines would be redundant against the virus. Vaccine escape happens when the virus changes so it dodges the full effect of the vaccine and continues to infect people.   How can we contribute to stop the emergence of new strains?   The primary thing to stop new mutations is to stem the spread of the virus. As mentioned earlier, the more the virus replicates, the more chance that mutations occur. Looking at the public trends in Sri Lanka even though we are learning to adapt to the “new normal”, it cannot be “business as usual”. Strict discipline needs to be maintained in wearing facemasks and social distancing. Public gatherings need to be minimised, which doesn’t appear to be happening in a satisfactory manner. In an attempt at reviving the tourism sector of Sri Lanka after keeping our borders closed to tourists for nearly nine months, Sri Lanka has opened its borders for tourists, with a maximum of 2,500 tourists permitted to enter each day. In light of this decision, it is even more important that we stay extra vigilant against both old and new strains of the virus, because ultimately it is our own selves that need to come together to defeat Covid-19.   (The writer is a medical officer currently attached to a government hospital. His experience spans across the medical profession as a medical practitioner, and across the pharmaceutical and surgical equipment industry. He also possesses an MBA and a Diploma in Economics. Having represented his university rugby team in international tournaments, he also has a special interest in sports medicine)

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Discover Kapruka, the leading online shopping platform in Sri Lanka, where you can conveniently send Gifts and Flowers to your loved ones for any event. Explore a wide range of popular Shopping Categories on Kapruka, including Toys, Groceries, Electronics, Birthday Cakes, Fruits, Chocolates, Automobile, Mother and Baby Products, Clothing, and Fashion. Additionally, Kapruka offers unique online services like Money Remittance, Astrology, Medicine Delivery, and access to over 700 Top Brands. Also If you’re interested in selling with Kapruka, Partner Central by Kapruka is the best solution to start with. Moreover, through Kapruka Global Shop, you can also enjoy the convenience of purchasing products from renowned platforms like Amazon and eBay and have them delivered to Sri Lanka.Send love straight to their heart this Valentine's with our thoughtful gifts!


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