The World Health Organization (WHO) has designated the mu SARS-CoV-2 strain, first detected in Colombia, as a "variant of interest" adding in its weekly bulletin that it will be monitoring the variant's spread.
According to WHO, the mu variant was first detected in Colombia in January.
Variants of interest have been found to have genetic changes that affect virus characteristics including transmissibility, disease severity and immune escape. Variants of interest differ from variants of concern, which have been found to cause a decrease in effectiveness of public health measures, vaccines or therapeutics.
"[Mu] has been designated as a Variant of Interest as it has some mutations that need to be studied for their potential impact on the body’s immune response. Data shared with the WHO Virus Evolution Working Group indicate that immunity developed through prior infection or vaccination may not be as strong against this variant. More studies are needed to confirm this," WHO said in a statement.
"The Mu variant has a constellation of mutations that indicate potential properties of immune escape. Preliminary data presented to the Virus Evolution Working Group show a reduction in neutralization capacity of convalescent and vaccine sera similar to that seen for the Beta variant, but this needs to be confirmed by further studies," WHO said in its weekly bulletin.
Other variants of interest include eta, iota, kappa and lambda. Like mu, lambda was also first detected in South America, in Peru. Iota was first detected in the U.S. in November.
"The circulation of the Mu variant has been declining globally, and less than 0.1% of currently shared sequences are of this variant," WHO said. "However, its prevalence in Colombia and Ecuador been increasing in recent weeks. WHO will closely follow the epidemiological evolution of this variant, along with studies on its impact."
The news comes as the U.S. continues to battle the spread of the delta variant, which remains the dominant strain in the country after first being reported in India.
The delta variant was designated by the WHO as a variant of interest in early April, and became a variant of concern May 11.