An overview of the current variant of SARS-CoV-2 virus leading to the continuity of the current pandemic situation.
Origin of Pandemic & Succeeding Omicron
With the emergence of the current pandemic of respiratory illness all over the world due to transmission of an infectious disease,COVID-19. It was first reported on 1st December,2019 and is said to have originated from an animal and gradually caused illness in humans due to continued mutation. It is spread through droplets and particles released into the air when an infected person breathes, talks or sneezes. Larger droplets fall to the ground within a few seconds, but tiny infectious particles can linger in the air and accumulate in indoor places with overcrowding and poor ventilation. The patient initially may be asymptomatic in mild conditions but if the infection proceeds further they may develop symptoms of cough,fever with chills, dyspnea,sore throat,ageusia and anosmia with additional associated ones being diarrhoea, nausea, vomiting,malaise, headache.
The Omicron Virus,B.1.1.529 variant was first reported to WHO from South Africa on 24 November 2021. The first known confirmed B.1.1.529 infection was from a specimen collected on 9 November 2021. The exact transmissibility of the variant is not yet known,compared to other variants. It multiples approximately 70 times faster than delta variant in the bronchi,but it’s severity is considered to be 91percent less as compared to the previous strains with hospitalization reduced to 51percent. It can lead to reinfection.
Astonishing Anatomy
During the discovery of the Alpha variant back in November 2020, scientists had very little knowledge about it’s mutations and it’s association with the behavioural pattern. Now with the subsequent years passing by and discovering new knowledge scientists have researched into its detail. They have been able to link some of the Omicron variant’s mutations to the mechanisms which has caused it’s spread, quickly and effectively.
Omicron virus hosts twice as many mutations as other variants of concern. There are 13 mutations on its spike protein that are rarely seen among other variants. This has led to a difference in the anatomy of the omicron variant from the rest of the variants. This includes four ways leading to this change,three of which have helped the virus evade our immune systems causing it to be more infectious, while the fourth may have led it to produce more mild diseases. Other variants include attack of antibodies by binding to the spike protein of the virus,whereas omicron has mutations to amino acids in two regions of spike,the receptor binding domains and N terminal binding domains. Thus the neutralizing effect is reduced.
In the preceding variants three amino acids on Receptor binding domains were mutated, altering each of them just enough to prevent some antibodies from recognizing it. But Omicron recides 15 receptor binding domain mutations, mainly on the prime antibody binding sites in a disguised form in order to prevent many more antibodies.
The spike protein has two subunits to separate as the infection of virus to the cell takes place. In older variants they were attached and frequently split too early.
The spikes S1 and S2 are loosely attached which allow them to split apart quickly so the spike can bury itself in a human cell when the virus encounters one,this may also lead to the split of viruses prematurely before nearing the cell.
The older virus variants relied on a surface protein of human cells called TMPRSS2 to help it break through the cell membrane,whereas omicron does not rely on it,instead uses only ACE2 to get inside.
Last but not the least,the fourth change which involves vulnerability to a part of our bodily defenses,the innate immune system. It is said that this vulnerability may prevent it from spreading into the deeper organs.
Clinical features, Diagnosis & Treatment
Omicron Virus possesses clinical features like loss of taste and smell similar to the delta variant with comparatively reduced severity.A characteristic feature of omicron variant is night sweats. A study performed by the Center for Disease Control found that the most commonly reported symptoms were cough, fatigue, and congestion or runny nose making it difficult to distinguish from a less damaging variant or other viruses. Less common symptoms were found consisting of sore throat, headache, aches, pains, diarrhoea,skin rash discolouration of fingers or toes and red or irritated eyes. Sometimes they may show serious symptoms like dyspnea, loss of speech or mobility, confusion,chest pain. If anybody possesses any of these symptoms then they should urgently head forward for COVID testing.
Less common symptoms were found consisting of sore throat, headache, aches, pains, diarrhoea,skin rash discolouration of fingers or toes and red or irritated eyes. Sometimes they may show serious symptoms like dyspnea, loss of speech or mobility, confusion,chest pain. If anybody possesses any of these symptoms then they should urgently head forward for COVID testing.
It is of the saying that S-gene target failure is suggestive of Omicron differentiating it from Delta. The identification can also be performed by sequencing and genotyping. Rapid antigen testing is also a diagnostic technique but has very little evidence.To ensure prevention,WHO recommended that people should continue to maintain ventilation, avoid overcrowding and close contact, wear well-fitting masks, clean hands frequently, and get vaccinated.
Remdesivir and Tocilizumab may be used in its treatment protocol for patients with moderate to severe illness. Remede Sivir may inhibit the virus multiplication. Tocilizumab is a monoclonal antibody which puts a stop to a possible cytokine storm.
Conclusion
It is of assumption that the current wave is because of omicron according to epidemiological and scientific evidence. Hopefully once RT-PCR tests which can indicate omicron’s presence are made available, distinguishing treatment would become easier. With the ongoing pandemic situation cases are turning milder compared to the second wave,thus many of whom are home quarantined with over the counter medication. Symptomatic management is of utmost importance among the medical fraternity. There is yet much to be researched and discovered for enhancing the current situation. Hopefully with new discoveries and vaccination dosage the situation will be brought to control in the future.
Pratiksha Baliga, Youth Medical Journal 2022
References
[1]MMWR, C. D. C. (2021, December 16). SARS-COV-2 B.1.1.529 (omicron) variant – united states, December 1–8, 2021. Centers for Disease Control and Prevention. Retrieved February 21, 2022, from https://www.cdc.gov/mmwr/volumes/70/wr/mm7050e1.htm
[2]Scudellari, M. (2022, February 11). Omicron’s surprising anatomy explains why it is wildly contagious. Scientific American. Retrieved February 21, 2022, from https://www.scientificamerican.com/article/omicrons-surprising-anatomy-explains-why-it-is-wildly-contagious/
Youth Medical Journal 