Q&A: What is the Mu Covid-19 variant and should we be worried? 

A pedestrian walks past a supermarket with Covid-19 and social distancing warning posted.

What is the Mu variant of Covid 19?

The Mu or B.1.621 variant was added to the World Health Organisation variants of interest list in recent days. It originated in Columbia where it now makes up 39% of cases. The WHO is monitoring this because of emerging evidence it can evade immunity provided by vaccines and antibodies.

The WHO’s weekly update said early data shows “a reduction in neutralization capacity of convalescent and vaccinee sera similar to that seen for the Beta variant”. However, it said further study is needed to confirm suspected similarities with the South African variant.

Is Mu in Ireland?

The GisAid variant tracker shows four cases reported from Ireland. Laboratories in Britain reported 65 cases including six in Northern Ireland. 

The tracker shows up to Friday the variant was found in 46 countries across North and South Americas, Europe and Asia. It makes up 0.5% of all cases worldwide according to the outbreak.info tracker linked to GisAid.

How worried should we be?

Dr Cillian de Gascun, director of the National Virus Reference Laboratory said on Friday there is “no real suggestion that it will be capable of out-competing Delta at this stage”. 

He pointed to a detailed study done by Public Health England which found it “appears unlikely that it is more transmissible” than the Delta variant.

This study notes similarities between this variant and the Beta variant but says the level of threat will depend on its growth and expansion. There were previously serious concerns about Beta in Ireland, but a combination of travel restrictions and public health tracing neutralised this.

What happens next?

Virologists and public health doctors here and elsewhere will monitor this variant. They will also be watching to see how it affects people compared to the Delta variant.

The WHO said: “The epidemiology of the Mu variant in South America, particularly with the co-circulation of the Delta variant, will be monitored for changes.” 

If they think this variant poses a great threat, it could be updated to a Variant of Concern.

The USA has the highest number of cases currently. However, Anthony Fauci, chief medical advisor there, told  The New York Times: “Bottom line, we are paying attention to it. We take everything like that seriously, but we don't consider it an immediate threat right now.” The GisAid trackers show Mu may have peaked in South America already, with Columbian scientists telling the media they are more concerned about Delta.

Why are we still seeing new variants?

Low vaccine uptake in many countries mostly due to lack of access is allowing the virus to continue mutating. In Colombia, for example, just 35% of the adult population are vaccinated according to the Bloomberg Vaccine Tracker.