How Many COVID Variants Are There As Mu Added to WHO Watch List

On Monday, the World Health Organization (WHO) added the Mu variant, or B.1.621, to its COVID variant of interest list.

The strain of the virus was first discovered in Colombia at the start of this year. Since then it has been found in at least 39 countries, mostly in South America, and Europe.

WHO and the Centres for Disease Control and Prevention (CDC) currently have three categories of COVID variants that make up their watch lists: variants of interest, variants of concern, and variants of high consequence.

The addition of Mu to the WHO watchlist was followed by a spike in Google users asking how many variants of COVID there are currently and how dangerous Mu is, according to Google Trends. The easiest way to determine this is to look at how variants of interest, variants of concern, and variants of high consequence are defined.

Genomic sequencing of the virus allows researchers to track and monitor the evolution of SARS-CoV-2 (the virus that causes COVID-19) and the mutations it undergoes. This includes changes that could help the virus evade detection by testing or avoid the protection offered by vaccination.

A SARS-CoV-2 variants with these properties, or with the potential to do harm in other ways, is identified by health organizations as a variant of interest.

The Mu variant has been added to the "interest list" as it has been identified as possessing a cluster of mutations that might help it slip past the immune response acquired by vaccination. It joins four other variants of interest, Eta, Iota Kappa, and Lambda.

These variants of interest are currently undergoing further investigation, and may ultimately leap up to the next severity level: the designation of "variant of concern."

The variants of concern list currently includes variants Alpha, Beta, Delta, and Gamma.

The CDC says that the variant of concern list consists of SARS-CoV-2 variants for which "there is evidence of an increase in transmissibility, more severe disease, a significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures."

This essentially means that these variants make people sicker and are more contagious than the variants of interest seem to be.

The final list of SARS-CoV-2 variants and the most severe is "variants of high consequence."

The CDC defines this as a variant for which there is "clear evidence that prevention measures or medical countermeasures have significantly reduced effectiveness relative to previously circulating variants."

To make this list a variant would have to demonstrate the ability to remain undetected by testing, show significant resistance to immunity offered by vaccination, and cause severe illness.

Fortunately, there are currently no SARS-CoV-2 variants that meet the extreme criteria needed to reach the variants of high consequence list.

Vaccination in Bali
A health worker administers the Sinovac COVID vaccine in Denpasar, Indonesia's Bali island, on September 2, 2021. The WHO added the Mu variant to its list of interest thanks to the possibility it could evade immunity provided by the shot. SONNY TUMBELAKA/AFP via Getty Images/GETTY