Laboratório de Bioinformática, Laboratório Nacional de Computação Científica, Petrópolis, Brazil.
Departamento de Genética, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Microb Genom. 2022 Sep;8(9). doi: 10.1099/mgen.0.000859.
During the first semester of 2021, all of Brazil has suffered an intense wave of COVID-19 associated with the Gamma variant. In July, the first cases of Delta variant were detected in the state of Rio de Janeiro. In this work, we have employed phylodynamic methods to analyse more than 1 600 genomic sequences of Delta variant collected until September in Rio de Janeiro to reconstruct how this variant has surpassed Gamma and dispersed throughout the state. After the introduction of Delta, it has initially spread mostly in the homonymous city of Rio de Janeiro, the most populous of the state. In a second stage, dispersal occurred to mid- and long-range cities, which acted as new close-range hubs for spread. We observed that the substitution of Gamma by Delta was possibly caused by its higher viral load, a proxy for transmissibility. This variant turnover prompted a new surge in cases, but with lower lethality than was observed during the peak caused by Gamma. We reason that high vaccination rates in the state of Rio de Janeiro were possibly what prevented a higher number of deaths.
2021 年上半年，巴西各地均遭受了与伽马变异株相关的 COVID-19 疫情的强烈冲击。7 月，里约热内卢州首次检测到了德尔塔变异株。在这项工作中，我们采用系统发育动力学方法，对截至 9 月在里约热内卢收集的超过 1600 份德尔塔变异株基因组序列进行了分析，以重建该变异株如何超过伽马变异株并在全州范围内传播。德尔塔变异株出现后，最初主要在该州人口最多的同名城市里约热内卢传播。在第二阶段，传播发生在中程和远程城市，这些城市成为新的近距离传播中心。我们观察到，伽马变异株被德尔塔变异株取代可能是因为其病毒载量更高，这是传染性的一个指标。这种变异株的更替引发了新的病例激增，但致死率低于伽马变异株引发的高峰时的水平。我们认为，里约热内卢州高的疫苗接种率可能是导致死亡人数较少的原因。
