Mu variant: Newly classified by WHO as a SARS-CoV-2 variant of interest

A VOI is classified based on factors such as genetic changes that are predicted or known to affect virus characteristics such as transmissibility, disease severity, immune escape etc. A VOI represents a lower level of concern than a variant of concern (VOC) such as Alpha, Beta or Delta, which are associated with factors such as an increase in transmissibility or detrimental change in epidemiology, etc.

The WHO assessment said the Mu variant has a constellation of mutations that indicate potential properties of immune escape. “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,” it said.

The global prevalence of the Mu variant among sequenced cases has declined and is currently below 0.1%, the WHO said. However, prevalence in Colombia (39%) and Ecuador (13%) has consistently increased.

“The reported prevalence should be interpreted with due consideration of sequencing capacities and timeliness of sharing of sequences, both of which vary between countries,” it said. “… The epidemiology of the Mu variant in South America, particularly with the co-circulation of the Delta variant, will be monitored for changes.”

A report in The Guardian said cases have also been reported in the UK (at least 32), Europe, the US and Hong Kong. The Mu variant was added to Public Health England’s list of variants under investigation in July.