More than 300 million confirmed cases have been reported since the COVID-19 pandemic emerged two years ago. The original COVID-19 virus (SARS-CoV-2) has evolved several times, leading to variants with different transmissibility, pathogenicity, and immune evasion. In addition to the Alpha, Beta, Gamma, and Delta variants, a new variant named Omicron was reported two months ago. Because of its very high transmissibility, large outbreaks have been recorded recently in different parts of the world. For instance, around a million cases per day are currently being reported in the USA, breaking all previous records. Similar waves have also been reported in different parts of Europe.
Omicron is more infectious than the other variants, with an increased risk of reinfection. These characteristics result from the high number of mutations that happened to its genomic sequence. In comparison to those observed in the other four COVID-19 variants, the spike mutations identified in Omicron outnumber them by three to four times. As a result, the early doubling time of Omicron was calculated to be 1.2 days compared to 1.7 and 1.5 days for the Beta and Delta variants, respectively. Fortunately, it has been reported that Omicron causes less severe disease. Otherwise, the world would have suffered devastating consequences.
There are several strategies to prevent the spread of the Omicron variant. Some focus on interrupting the transmission of the variant by maintaining strict public health prevention measures, including PPE-use and physical distancing. Other strategies aim to improve vaccine coverage despite the doubts about their effectiveness against this variant. Studies have, however, shown that the COVID-19 vaccines currently in use remain effective to a certain extent. This highlights the need to develop Omicron-specific vaccines. In terms of diagnostics, Omicron is detectable by the widely used PCR techniques like the other variants.
Despite the accumulated knowledge about all COVID-19 variants, many questions remain unanswered about Omicron and its origin. Inevitably, more variants will emerge in the future. It is, however, not known if they will originate from Omicron. Unfortunately, it will be challenging to deal with variants with both strong transmissibility and pathogenicity.
References:
- Xuemei, H. et al. (2021). SARS-CoV-2 Omicron Variant: Characteristics and Prevention. MedComm, 2(4): 838-845. https://doi.org/10.1002/mco2.110.
- CDC COVID-19 Response Team (2021). SARS-CoV-2 B.1.1.529 (Omicron) Variant - United States. MMWR, 70(50): 1731-1734. https://doi.org/10.15585/mmwr.mm7050e1.