Current Dominant COVID-19 Strain
The current dominant strain of COVID-19 is the Omicron variant and its subvariants, which have displaced previous variants through successive waves of infection worldwide throughout 2022-2023. 1
Evolution of SARS-CoV-2 Variants
Original SARS-CoV-2
- Initially identified in late 2019, SARS-CoV-2 is a single-stranded RNA virus belonging to the Coronaviridae family 2
- The virus has demonstrated significant ability to mutate and evolve through:
- Genetic recombination
- Natural selection
- Mutations in the receptor-binding domain 2
Emergence of Omicron
- Omicron emerged in late 2021 and quickly became the dominant variant globally 1
- It is characterized by:
- Multiple mutations in the viral genome
- Enhanced viral fitness
- Greater transmissibility
- Ability to evade immunity from prior vaccination or infection 3
Current Omicron Subvariants
The Omicron variant has continued to evolve, producing multiple subvariants with distinct characteristics:
- Main Omicron Sublineages: BA.1, BA.2, BA.3, BA.4, and BA.5 have all circulated globally 3
- Recombinant Variants: Several recombinant subvariants have emerged, including XBB, XBD, and XBF 3
- Newer Subvariants: BA.2.12.1, BA.4, and BA.5 have demonstrated increased immune evasion capabilities 4
Key Characteristics of Current Strains
Enhanced Immune Evasion
- BA.4/5 subvariants show 4.2-fold greater resistance to sera from vaccinated and boosted individuals compared to earlier variants 4
- Mutations at specific spike protein locations (L452, F486V, R493Q) facilitate escape from antibodies while maintaining receptor affinity 4
Transmissibility
- Current Omicron subvariants demonstrate higher transmissibility than previous variants 3
- Transmission occurs efficiently via:
- Respiratory droplets
- Direct contact
- Potential aerosol propagation in closed environments 2
Clinical Impact
- Despite increased transmissibility, current variants generally cause less severe disease in vaccinated individuals 1
- However, they remain capable of causing serious illness in:
- Elderly individuals
- Those with major medical comorbidities
- Unvaccinated populations 2
Public Health Implications
- COVID-19 has demonstrated continuous transmission throughout the calendar year, affecting populations globally regardless of season 5
- Testing and surveillance must remain active year-round to detect and respond to outbreaks 5
- Vaccination and boosters continue to be important in reducing disease severity, hospitalization, and death from current variants 1
- Only certain therapeutic antibodies (notably bebtelovimab) retain full potency against newer Omicron subvariants 4
Prevention Strategies
- Ongoing vaccination programs rather than seasonal campaigns are recommended 5
- Continued vigilance with personal protective measures remains important:
- Hand hygiene
- Appropriate mask use when indicated
- Social distancing in high-risk settings 5
- Special attention to protecting vulnerable populations regardless of season 5
The rapid evolution of SARS-CoV-2 continues to present challenges for public health response, requiring ongoing surveillance and adaptation of prevention and treatment strategies as the virus continues to evolve.