Insights into the limited global spread of the immune evasive SARS-CoV-2 variant Mu

Abstract

SARS-CoV-2 Variants of Concern (VOCs) continue to reshape the trajectory of the COVID-19 pandemic. However, why some VOCs, like Omicron, become globally dominant while the spread of others is limited is not fully understood. To address this question, we investigated the VOC Mu, which was first identified in Colombia in late 2020. Our study demonstrates that, although Mu is less sensitive to neutralization compared to variants that preceded it, it did not spread significantly outside of South and Central America. Additionally, we find evidence that the response to Mu was impeded by reporting delays and gaps in the global genomic surveillance system. Our findings suggest that immune evasion alone was not sufficient to outcompete highly transmissible variants that were circulating concurrently with Mu. Insights into the complex relationship between genomic and epidemiological characteristics of previous variants should inform our response to variants that are likely to emerge in the future.

Genomic epidemiology of circulating SARS-CoV-2 variants during first two years of the pandemic in Colombia

“…4). Comparing variants, Mu showed the highest R e values indicating higher 4/24 transmissibility than Alpha, Gamma, Lambda, and even Delta, which had been reported as dominant variants in the countries they have circulated 30 . This suggests that once Mu emerged in Colombia, it out-competed the other variants and became the dominant one.…”

Genomic epidemiology of SARS-CoV-2 variants during the first two years of the pandemic in Colombia

“…These values are congruent with previous studies for the two first periods, with medians from 1.07 to 2.13 for the first period and from 0.99 to 1.09 for the second one, respectively 4 . Comparing variants, Mu showed the highest R e values indicating higher transmissibility than Alpha, Gamma, Lambda, and even Delta, which had been reported as dominant variants in the countries they have circulated 58 . This suggests that once Mu emerged in Colombia, it out-competed the other variants and became the dominant one.…”

Genomic epidemiology of circulating SARS-CoV-2 variants during first two years of the pandemic in Colombia

“…All analyzed variants recovered peaks >1, suggesting that a variant's spread was greater than another during a specific period (Figure S4). Comparing variants, Mu showed the highest R e values indicating higher transmissibility than Alpha, Gamma, Lambda, and even Delta, which had been reported as dominant variants in the countries they have circulated 30 . This suggests that once Mu emerged in Colombia, it out-competed the other variants and became the dominant one.…”