The Omicron variant is a variant of SARS-CoV-2, the virus that causes COVID-19. As of December 2021, it is the newest variant. It was first reported to the World Health Organization (WHO) from South Africa on 24 November 2021.On 26 November 2021, the WHO designated it as a variant of concern and named it “Omicron”, the fifteenth letter in the Greek alphabet.
The variant has an unusually large number of mutations, several of which are novel (see § Mutations) and a significant number of which affect the spike protein targeted by most COVID-19 vaccines at the time of the discovery of the Omicron variant. This level of variation has led to concerns regarding its transmissibility, immune system evasion, and vaccine resistance, despite initial reports indicating that the variant causes less serious disease than previous strains. The variant was quickly designated as being “of concern”, and travel restrictions were introduced by several countries in an attempt to slow its international spread.
Compared to previous variants of concern, Omicron is believed to be far more contagious (spreading much quicker), and spreads around 70 times faster than any previous variants in the bronchi (lung airways), but it is less able to penetrate deep lung tissue, and perhaps for this reason there is a considerable reduction in the risk of severe disease requiring hospitalisation.[7] However, the extremely high rate of spread, combined with its ability to evade both double vaccination and the body’s immune system, means the total number of patients requiring hospital care at any given time is still of great concern.
The new variant was first detected on 22 November 2021 in laboratories in Botswana and South Africa based on samples collected on 11–16 November. The first known sample was collected in South Africa on 8 November. In other continents, the first known cases were a person arriving in Hong Kong from South Africa via Qatar on 11 November, and another person who arrived in Belgium from Egypt via Turkey on the same date. As of 16 December 2021, the variant has been confirmed in more than 80 countries. The World Health Organization estimated that by mid-December, Omicron likely was in most countries, whether they had detected it or not.
Nomenclature
On 26 November, the WHO’s Technical Advisory Group on SARS-CoV-2 Virus Evolution declared PANGO lineage B.1.1.529 a variant of concern and designated it with the Greek letter omicron. Greek letters are used to identify variants of SARS-CoV-2. The WHO skipped the preceding letters nu and xi in the Greek alphabet to avoid confusion with the similarities of the English word “new” and the Chinese surname Xi. The previous designation was for the “variant of interest” mu.
Possibly due to a lack of familiarity with the Greek alphabet among some English speakers and the relative frequency of the Latin prefix “omni” in other common speech, the name of the variant has also occasionally been mispronounced and misspelled as “Omnicron”.
The GISAID project has assigned it the clade identifier GR/484A, and the Nextstrain project has assigned it the clade identifier 21K
Signs and symptoms
As of 28 November 2021, the World Health Organization’s update states, “There is currently no information to suggest that symptoms associated with Omicron are different from … other variants”.
A study performed between 1 and 7 December by the Center for Disease Control found that: “The most commonly reported symptoms [were] cough, fatigue, and congestion or runny nose”.
Research published in London on 25 December 2021 suggested the most frequent symptoms stated by users of the Zoe Covid app were “a running nose, headaches, fatigue, sneezing and sore throats.”
A unique reported symptom of the omicron variant is night sweats.