Mu variant: Is it a cause for concern? What we know so far

Mu may be more vaccine resistant than other Covid strains in circulation although further testing is needed to confirm this, said the WHO

Mu (or B.1.621) is the fifth strain of Covid labeled as a variant of interest by the World Health Organisation (WHO) (Getty Images)

What is the new variant?

A novel variant of Covid-19 has found its way into the UK with 55 cases so far identified in England.

Mu (also known as  B.1.621) is the fifth strain of coronavirus to be labeled by the World Health Organisation (WHO) as a variant of interest.

Where did it originate?

It was first discovered in Colombia in January 2021, and is currently particularly prevalent there and in neighbouring Ecuador where it is responsible for around 39 per cent and 13 per cent of infections, respectively.

Global prevalence of Mu, on the other hand, remains low among sequenced Covid cases at below 0.1 per cent but the variant is beginning to make its way over to European countries.

According to WHO, Reports on the variant’s prevalence should be “interpreted with due consideration” due to the low sequencing capacity of many countries.

Is it more resistant to vaccines?

Public Health England (PHE) said in July that there was no evidence to suggest Mu would be likely to cause more serious illness or make vaccines less effective.

However, WHO have since said that the variant has mutations, which could make it more vaccine resistant than strains of the virus currently in circulation. They did add however that further studies will be needed to confirm this.

WHO said: “Since its first identification in Colombia in January 2021, there have been a few sporadic reports of cases of the Mu variant and some larger outbreaks have been reported from other countries in South America and in Europe.

“Although the global prevalence of the Mu variant among sequenced cases has declined and is currently below 0.1 per cent, the prevalence in Colombia (39 per cent) and Ecuador (13 per cent) has consistently increased.

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

Currently, there are four coronavirus variants of concern in circulation. These are the Alpha variant, seen in 193 countries, Beta in 141, Gamma in 91 and Delta in 170 countries. Mu meanwhile, marks the fifth variant of interest.

Over 4,500 sequences have been designated as Mu in the past four weeks, as of 29 August.

Most of these cases have been reported in the US (2,065), Colombia (852), Mexico (357) and Spain (473), although the figures will be affected by both sequencing capacity, surveillance and the total number of cases in a particular area.