SARS-CoV-2 variant transmission in a community-health population (Mexico City, Mexico)

The SARS-CoV-2 variant, B.1.1.519, arose in North and Central America, circulating primarily in Mexico. We demonstrate that this variant peaked during the second wave of COVID-19 in Mexico City in the spring of 2021. This variant is likely more infectious, attributed to mutation in the RBD of the spike protein T478K also seen in the alpha variant (B.1.1.7). However the time dynamics of the spread of this variant drastically changed upon the introduction of delta (B.1.617.2) to the country in which we observe a shift from 0% in May 2021 to 55% delta in the span of one month. Since the delta variant has dominantly spread across the globe, we investigated the increasing frequency of the Mexico variant , B.1.1.519, in the public community within Mexico City. Once present, the delta variant was 78% of the Mexico City catchment in July 2021, a time which marked the commencement of Mexicos third wave. Our data supports the growing concern that the delta variant is closely associated with the massive infection spread of the VOC in Central and South America. While the T478K mutation, also seen in the alpha variant, has evidence for increased transmissibility, these data suggest that the delta variant shows overall increased fitness seeing as it outcompeted the B.1.1519 this Mexico community.