A virus is just about the simplest replicating machine possible, with scientists unable to agree if they are living or non living things. This is because viruses do not have all the cellular machinery required for self-replication, only the genetic material within a protein capsule. They infect and hijack the cellular machinery of the host organisms in order to replicate. The entire genetic code is not copied perfectly each time, and these changes cause mutations. Some of these mutations are more effective at replicating than others, leading to the emergence of variants.
A virus can make hundreds of copies of itself in a single infected host cell, but for the virus to replicate, it needs a live host. If the host is dead, the virus also cannot replicate. Chandrakant Lahariya, vaccinologist, public health practitioner and author of the book Till We Win: India's Fight Against The Covid-19 Pandemic, tells us, "Because of the evolutionary process, different forms of the virus will emerge. If a virus causes severe disease, it kills the host. Then the chances of transmission are low, so that is not in the best interest of the virus."
The data acquired so far from South Africa suggests that the Omicron variant is more transmissible, but causes less severe diseases. A study conducted by researchers from the University of Hong Kong provided additional evidence on similar lines, indicating that the Omicron variant multiplies 70 times faster than the currently dominant Delta variant, but causes milder illnesses in comparison. The dominant variant, is the variant of COVID-19 that has the most infections around the world.
Comparative prevalance of the variants, Omicron is represented in red in the bottom right. (Image credit: Nextstrain)
Lahariya explains how a more transmissible but less severe variant can emerge as a pandemic progresses, "Any pathogen wants to multiply and go to different hosts. All the variants which emerge and have more severity, which essentially means a severe disease in the person, and killing of the host, those strains would not circulate well. This is because the person will die, or healthcare workers will identify the severe disease and then the transmission will be stopped. But the strains which cause a mild disease, and have a higher transmissibility, are more likely to go undetected and pass on to different set of people. Those will be the strains that will remain in the end. It seems like that is the pattern with the Omicron variant, it causes a mild disease and has a high transmissibility. The mild disease and asymptomatic cases will be undetected, and that provides a perfect platform for the virus to pass on, and also such strains are likely to last longer."
Dr Ashutosh Shukla, Senior Director of Internal Medicine and Medical Advisor at Max Hospital, Gurgaon explains how over the course of a pandemic, a virus is pushed towards causing less severe disease, but increasing in transmissibility, "This particular strain (the Omicron variant) causes less severe disease compared to the Delta variant. So it is the way a pandemic kind of comes downhill, usually the disease intensity is higher (at the start), and then gradually and slowly the intensity of the disease keeps coming down. But, since the transmissibility is higher, there is a concern over the Omicron variant, because it will rapidly spread across the globe."
One strain of the Omicron variant, does not always register on conventional RT-PCR tests, and is unofficially called the "stealth Omicron" by healthcare professionals. When then asked about the stealthiness of the Omicron variant, and the ability of other variants to dodge the tests designed to detect infections, Lahariya explains that this is because of the tendency of the virus to develop mutations as it rapidly replicates, instead of an external pressure by the diagnostics, which comes at a late stage of the infection, "No, the stealthiness of the virus is not related to diagnostics or treatment, it is the normal process for the virus to evolve and develop mutations. Diagnostics and therapies play a role only when the person is already infected, so they do not interfere with the processes of the virus."
The mutations that give rise to more severe infections are just not very helpful for the virus that just wants to make copies of itself. In order to be more successful in life, the virus has to evolve variants that cause less sever diseases, that keep the host alive. Jared Auclair, associate associate teaching professor of chemistry and chemical biology at Northeastern University says, "If you think about a virus, what's the purpose? What's the virus trying to do? It's trying to stay alive. If the virus kills someone, if it kills the host, it dies with the host. So it totally defeats the purpose. The easiest thing for the virus to do is to stay in the same person for as long as possible. It's less work, so to speak, as opposed to hopping to another host."
Though it is still in the early weeks since the emergence of the Omicron variant, early data suggests that the variant is effective at reinfecting those who have previously been infected by SARS-CoV-2, as well as dodging the vaccines. A study by researchers from Oxford University also showed a reduce capacity of the immune response in those who have received conventional vaccines, for producing antibodies that could neutralise the Omicron variant. A WHO report based on multiple studies also indicated a reduced efficacy of conventional vaccines against the Omicron variant.
The virus is going to evolve differently in the hosts who have been vaccinated or have been previously infected, as compared to the general population. This is because the virus may have to adapt to work around the immune system fighting against it. Observing such changes in the virus, may be a sign that the tactics of the humans are actually working. The emergence of the Omicron variant, and similar variants in the future can be a sign that humans are actually winning the fight against COVID-19.
Mansoor Amiji, university distinguished professor of pharmaceutical sciences and chemical engineering at Northeastern University says, "It is, to some degree, a cat-and-mouse game, but it's an evolutionary process for the virus. It's like, you know, 'these guys are out to get me, I will try to change myself to become better, to resist'. We are now influencing the virus to do these types of variants in a much shorter timescale because it's feeling the pressure. What we are doing with vaccines is shortening that time between pandemic and endemic."
Researchers are still struggling to explain how the Omicron variant will change the course of the pandemic. At present time, the Delta variant remains the dominant variant, with the Omicron variant spreading rapidly. However, considering the progression of previous pandemics, the emergence of strains that are highly transmissible while causing less severe diseases, can signal that an outbreak is moving towards its end.
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