According to the WHO’s weekly bulletin on the pandemic, the Mu variant “has a constellation of mutations that indicate potential properties of immune escape”. Preliminary data suggests it may evade immune defences in a similar way to the Beta variant first discovered in South Africa, the report adds, but this needs to be confirmed by further work.
The Mu variant was first identified in Colombia in January 2021. Since then, sporadic cases and some larger outbreaks have been recorded around the world. Beyond South America, cases have been reported in the UK, Europe, the US and Hong Kong. While the variant makes up less than 0.1% of Covid infections globally, it may be gaining ground in Colombia and Ecuador where it accounts for 39% and 13% of Covid cases respectively.
Scientists and public health officials are particularly eager to know whether the Mu variant is more transmissible, or causes more serious disease, than the Delta variant that is dominant in much of the world. “The epidemiology of the Mu variant in South America, particularly with the co-circulation of the Delta variant, will be monitored for changes,” the WHO bulletin states."