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Omicron Symptoms Timeline - Everything You Need to Know

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Omicron is a coronavirus variant, classified as a variant of concern that shares several mutations with previous variants.

Medically reviewed by

Dr. Shubadeep Debabrata Sinha

Published At May 30, 2023
Reviewed AtApril 16, 2024

Introduction:

The coronavirus disease 2019 (COVID-19) is a pandemic surging for almost two years. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified in 2019, and various variants emerged. These variants are classified into three categories:

  1. Variants of concern.

  2. Variants of interest.

  3. Variants under monitoring.

Four variants, Alpha, Beta, Gamma, and Delta, previously resulted in a new wave pandemic resulting in thousands of death. The Omicron variant (B.1.1.529) emerged on November 26, 2021, and is called the fifth variant of concern that immediately raised global concerns.

How Did Omicron Emerge?

The emergence of the Omicron variant was known on November 9, 2021, and the first variant was reported to WHO on November 24, 2021. At first, it was designated as a variant under monitoring (VUM). Two days later, it was categorized as a variant of concern (VOC) that recorded the shortest period of reclassifying a variant from VUM to VOC. Omicron was reported in 34 countries and areas, including Botswana, Hong Kong, South Africa, Israel, Belgium, Italy, and the USA.

The origin and evolution of the Omicron variant are yet to be investigated. The analysis of sequences of SARS-CoV-2 variants shows that Omicron is a lot different from other variants; hence difficult to identify its closest relative.

What Are the Symptoms of Omicron?

The symptoms include:

What Are the Characteristics of the Omicron Variant?

Characteristics of the Omicron variant:

  • Three variants of COVID-19 outbreaks have been recorded since 2020. Two among them are Beta and Delta variants.

  • The percentage of infections associated with Beta variants was shown to be approximately 50 percent, and the Delta variant raised to about 80 percent.

  • During its period of emergence, the transmission of the Delta was higher than the Beta.

  • In contrast to this rapid transmission, the percentage of Omicron infection reached 90 percent within 25 days of its evolution.

  • The doubling time calculated for Beta, Delta, and Omicron is 1.7, 1.5, and 1.2 days respectively.

  • These data reveal that the Omicron variant is more infectious than the Beta and Delta variants.

  • A population-based retrospective study in South Africa showed an increased risk of SARS-CoV-2 reinfection associated with Omicron.

  • The genomic sequence analysis of the Omicron variant showed a high number of non-synonymous mutations, including several changes in the spike that involved in transmissibility, disease severity, and immune escape.

  • More than sixty substitutions or deletions, or insertions were identified in the Omicron variant. Causing Omicron, a variant possessing the largest number of mutation sites of all SARS-CoV-2 variants known so far.

  • Within OrF1a, the Omicron harbors as six substitutions (K856R, L2084I, A2710T, T3255I, P3395H, and I3758V). And two deletions among a total of four amino acids (amino acid 2083 and amino acids 3674 to 3676).

  • Within ORF1b, the variant contains two substitutions (P314L and I1566V).

  • In addition, a P10S substitution and a three-residue deletion at positions 27-29 are observed in ORF9b.

  • For the structural proteins, there are one substitution (T9i) in the envelope (E), three substitutions (D3G, q19E, and A63T) in the membrane (M), and three substitutions and three residue deletion in the nucleocapsid (N) proteins, respectively.

  • The mutations mentioned above emerge along the whole viral genome. The remaining mutations, which account for over half of the total Omicron mutations identified, accumulate in the spike.

  • Compared with the other four VOC variants, the spike mutations identified in Omicron out-number by about three to four times.

  • The notable point in all five VOCs is that containing the amino acid change D614G in spike.

  • The Omicron variant also shares N501Y with alpha, Beta, and gamma variants which are believed to enhance binding between spike and angiotensin-converting enzyme 2 (ACE2) and induce higher transmissibility.

  • Omicron also has N679K and P681H mutations near the furin cleavage site. Incorporating basic amino acids around the furin cleavage site facilitates the cleavage spike into S1 and S2, enhancing fusion and virus infection.

  • The P681H mutation, also seen in the alpha variant, is known to enhance SARS-CoV-2 infectivity.

  • These mutations in the Omicron spike were also identified in other VOCs such as D614G, N501Y, K417N, P681H, and the residue-substitution of E484 that indicated a higher binding affinity with ACE2 enhancing transmissibility and pathogenicity and reduced neutralization ability by monoclonal antibodies and immune evasion.

What Are the Preventive Measures for Omicron Variant Infection?

Strategies to prevent the Omicron variant include:

1. Interruption of SARS-COV-2 Variant Spread: A detailed feature of Omicron is currently unclear. Noting the spike mutations in all VOCs, the Omicron might have evolved with the capacity to spread easily among people and the ability to resist currently available antibody treatments. This highlights the importance of preventive measures such as wearing masks, good ventilation, keeping physical distance, and washing hands. These measures have proven effective in halting the transmission of other variants and are also to be considered for Omicron. Also, early diagnosis and timely quarantine are key factors that minimize virus transmission during the pandemic. Therefore, improving diagnosis accuracy, isolation, and treatment is vital in interrupting the transmission of the Omicron variant.

2. Improving COVID-19 Vaccine Coverage: The rapid spread of Omicron was a signal of a new wave pandemic worldwide, as its influence was unclear. During the Omicron emergence, the vaccinated population was lower in percentage, which may accelerate the spread of Omicron. This led to the urgent need to increase vaccination coverage. The vaccines are proven effective in preventing severe diseases, hospitalizations, and death.

3. Developing Variant-Specific Vaccines: Reports have shown that SARS-CoV-2 is at higher risk of reinfection associated with the Omicron variant indicating its association with a substantial ability to evade immunity from prior infection. In addition, few studies showed that COVID-19 vaccines were less effective against Omicron when compared with other variants. This suggests further investigations are needed to improve vaccine efficiency.

Specific variant vaccines need to be developed based on a mutated spike to prevent Omicron infection and transmission.

Conclusion

Regarding the emergence of the Omicron variant, the origin, transmission, and immune potential are unclear. New Omicron variants might evolve due to their mutations. The continuous emergence of new variants has made it challenging to control COVID-19 infection. The basic protocols to prevent COVID-19 should also be followed for Omicron to prevent its infection. Vaccines help control disease severity, hospitalization, and death; hence, vaccinations are encouraged.

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Dr. Shubadeep Debabrata Sinha
Dr. Shubadeep Debabrata Sinha

Infectious Diseases

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