The World Health Organization announced it is now tracking a new coronavirus variant known as “mu,” or B.1.621. Early data suggest the variant is showing resistance to COVID-19 vaccines similar to the beta variant, which one recent study suggests is deadlier than all other variants.In its weekly epidemiological update published Tuesday, the WHO explained that mu was first identified in Colombia in January 2021 but officially flagged it as a variant of interest on Monday.Variants of interest usually cause “significant community transmission or multiple COVID-19 clusters, in multiple countries with increasing relative prevalence alongside increasing number of cases over time,...