COVID-19 in Latin America: Tracking the SARS-CoV-2 Mu (B.1.621) Variant: Epidemiology, Genomics, and Vaccine Resistance

In the wake of the COVID-19 pandemic, monitoring SARS-CoV-2 variants became critical to global health and efforts to curb virus spread. Over time, the emergence of more virulent and transmissible variants, which are less responsive to vaccines, intensified health concerns. In early 2021, Colombia detected a new variant, B.1.621, which quickly became the dominant strain in the country. After circulating for 7 months, the World Health Organization (WHO) labeled this Mu (B.1.621) variant as a “variant of interest” (VOI). This was due to spike mutations that helped the virus bypass our immune defenses. Notably, one mutation, E484K, was linked to decreased antibody sensitivity. Tests later revealed that the Mu variant resisted neutralization from immune responses approximately ten times more than the original B.1 lineage. This data underscores the need for genomic monitoring, continued vaccination, and booster shots to guard against new variants. This chapter summarizes current knowledge on the Mu variant, offering insights that might be applied to other emerging strains posing public health threats.