WHO says it’s watching Mu, a new COVID-19 variant of interest

The World Health Organization (WHO) has enough COVID-19 variants to worry about.

Now it’s keeping an eye on Mu, too.

The WHO says it’s monitoring a new coronavirus variant that was first detected in Colombia in January, adding a fifth entry to its official “variant of interest” list.

The variant has been named after the Greek letter Mu, though it also goes by the designation B.1.621. Brits pronounce Mu like a cat’s “mew,” while Americans pronounce it like a cow’s “moo,” according to the Cambridge Dictionary. But how you pronounce Mu is up to you.

WHO officials deemed Mu to be a variant of interest on Aug. 30 after it was detected in 39 different countries. They say the variant has a “constellation of mutations” that might make it more infectious, even among those with immunity.

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Preliminary data suggests that Mu might be capable of overcoming the defences of a vaccinated person, according to a weekly WHO update issued Tuesday, but more study is needed to confirm its ability to infect.

The WHO says Mu accounts for less than 0.1 per cent of global documented infections, although cases have been steadily rising in Colombia and Ecuador. Officials also point out that monitoring data isn’t perfect, and that the virus has also been seen in Europe and elsewhere in South America.

There are currently five variants of interest on the WHO’s watch list. There are also four variants of concern that are deemed to be a greater threat: Alpha, Beta, Gamma and Delta. The Delta variant has been responsible for many of the cases in North America.

Delta was a variant of interest until it was reclassified as a concern in May.