The surge in Covid-19 cases in China has global health authorities fearing the arrival of new variants. Over the past three months, more than 130 new Omicron sublines have been detected.
Majority in France and in the world for nearly a year, Omicron is the last variant qualified as “concerning” to have been listed by the World Health Organization (WHO). Since then, its sub-lineages such as BA.4 or BA.5 have been responsible for the latest epidemic outbreaks in Europe.
The first variants of Covid-19 appeared at the end of 2020. To survive in the body, a virus must multiply in cells by creating replicas. It is during this process of reproducing the genetic code that errors can occur, making the virus more transmissible and more resistant to humanitarian responses, including vaccines.
Alpha, Beta and Gamma
dits “worrying” by their increase in the transmissibility of the disease, the Alpha, Beta and Gamma variants can be detected following a PCR test by screening.
The first variant to be introduced into the world is Alpha, at the end of 2020. It becomes the majority in France in March 2021, one year after the first confinement, and is the source of increased contagiousness (30% more than the normal strain). The WHO has designated it as “formerly worrying variant” on March 2022.
After being listed in South Africa and Brazil respectively, the Beta and Gamma variants circulate at the same time, in the first half of 2021. They do not become the majority in place of Alpha, despite their contagiousness greater than 25% and 38% compared to the original strain. Both have been classified as “formerly worrying variant” on March 2022.
Delta et Omicron
The Delta variant, detected for the first time in India, is the cause of a major epidemic outbreak because of its high contagiousness (97% more than the initial strain). It appears in May 2021 and takes precedence over previous variants. In France, it represents more than 99% of cases from August. The WHO classifies it as “formerly worrying variant” more than a year later, in June 2022.
Latest variant of concern: Omicron, detected in mid-November 2021 in Botswana and South Africa. It is increasingly spreading, supplanting Delta and very quickly becoming the majority in France and around the world. So much so that new so-called “bivalent” vaccines used as a booster have been adapted to this variant.
Since then, almost all cases of Covid-19 screened have been linked to this strain. Omicron also produces a large number of sub-variants, each time responsible for a significant epidemic recovery. China is the latest example.