Paris - A new variant of Covid-19 detected in South Africa known as B.1.1.529 has caused flight bans and a scramble to determine vaccine efficacy.
It is the latest coronavirus strain to emerge since the start of the pandemic, including the currently dominant delta variant, which was first detected in India in October 2020.
Globally, delta has overtaken other strains of the virus in most countries and accounts for 99.8 percent of sequenced cases over the past 60 days according to the latest weekly report by the World Health Organization (WHO).
Next comes the gamma variant, which accounts for 0.1 percent of sequenced cases, followed by alpha and beta which each make up less than 0.1 percent.
What do we know about the B.1.1.529 coronavirus variant?
Lesser-known variants like mu and lambda are rarely sequenced.
However, the WHO says that at a regional and national level there are variations in which strains dominate, especially in certain South American countries where delta has been slower to spread.
The emergence of variants is a natural process that happens as the virus mutates to ensure its survival over time.
Most mutations have little or no impact on the virus's ability to infect or cause severe disease.
Factfile on SARS-CoV-2 variants of concern
But certain mutations can affect how easily the virus can spread, the degree of severity of the disease they cause and how well a vaccine can respond to them.
WHO experts following the evolution of the Covid-19 gathered Friday to determine whether it should be classified as "of concern" or "of interest".
They announced that it would take "several weeks" to understand how contagious B.1.1.529 is and the severity of the illness it can cause.
Currently, the WHO has classified only the alpha, beta, gamma and delta variants as being "of concern".
WHO says will take several weeks to understand new variant (Nov 26)
They are considered worrying because they are highly contagious or cause more severe illness.
Mu and lambda are considered "variants of interest" because their show genetic changes that mean they have potential to become more contagious, harder to detect, or cause more severe illness.
All variants are classified by "lineage" and have a specific spot in the family tree that originates with the first SARS-CoV-2 virus.
The delta variant is about twice as contagious as previous variants and vaccines are about 40 percent less effective at preventing infection from delta than from other variants.
Why does a virus mutate?
By Isabelle Tourné