**2.1 Variants**

The evolution of the SARS-CoV-2 has been continuous with several variants emerging with unusual frequency. Although the clinical picture is similar, these genetic mutations have meant the prolongation of the pandemic with numerous unsolved effects and challenges. Omicron (B.1.1.529), the last variant that originated in South Africa in November 2021 has been classified as a concern variant, which, like the previous variants, has generated globalized uncertainty. These genetic mutations can affect the gene encoding the Spike (S) antigen with effects on preventive and therapeutic strategies known so far. The gold standard for the identification of variants is the sequencing of the entire genome, although recently real-time PCR techniques have been developed for the detection of specific mutations that can facilitate their identification.

Studying the variants could help assess risks and develop better treatment and prevention strategies [12–17]. An international classification system has been established to distinguish emerging variants of this virus into variants of concern (VOC) and variants of interest (VOI), which are listed in **Table 1**.

The under surveillance and de-escalated variants are also included in this classification. The classification of SARS-CoV-2 variants is continually modified


**Table 1.** *COVID-19 variants.* according to the genetic mutations of the virus and the WHO, CDC, and ESDC guidelines [16, 17, 18].
