Against all expectations, the new variant was named after the 15th letter of the Greek alphabet, Omicron. The denomination from a Greek letter corresponds well to the system set up by the World Health Organization. However, two letters before Omicron, Nu and Xi, have not been attributed.

Indeed, since the appearance of variants, a nomenclature system has been set up, made up of letters and numbers, in order to “name and monitor the genetic lines of SARS-CoV-2”. At the same time, in order to facilitate the naming of these variants, the WHO recommended to name them using the name of the letters of the Greek alphabet, “more accessible to a non-scientific audience”.

Names from Greek letters are as well “easy to pronounce and non-stigmatizing” for the variants to follow and the variants of concern, justified the WHO. This system thus makes it possible to avoid naming the variant in relation to the geographical location where it was detected for the first time. Indeed, the Alpha variant, sequenced for the first time in the United Kingdom, was previously named “English variant”, just as the Delta variant was nicknamed the “Indian variant”.

In addition to these variants, there was the Beta variant, first listed in South Africa and the Gamma variant in Brazil. Respecting the order of the alphabet, other variants have been or are still being followed by the WHO. The Epsilon variant was thus discovered in California, in the United States. The Zeta variant was spotted in July in Rio de Janeiro, Eta was identified in the United Kingdom and Nigeria, Theta in the Philippines, Iota, New York, Kappa, India, Lambda in Peru and Mu, in Colombia.

Among these variants, only Lambda and Mu are still designated as “variants to follow”. Kappa, Iota, Eta and Epsilon were demoted as “variants under surveillance”. Zeta and Theta are no longer under surveillance. The Alpha, Beta, Gamma, Delta, and now Omicron variants are designated as variants of concern.

The B.1.1.529 variant in South Africa is therefore the 13th variant monitored by the World Health Organization. Following its naming system, the international agency should therefore have named this variant, Nu, letter coming after, Mu. However, it is not this one, nor the following one, the letter Xi, which were chosen, but Omicron.

The WHO justified this choice by pointing out that Nu could be too easily confused with “new”, new in english. As for Xi, the letter was not used, because it corresponds to a name that is too common. For the moment, Nu and Xi are therefore the only two letters of the alphabet that have been put aside by the WHO.