Genomic epidemiology of the SARS-CoV-2 epidemic in Brazil

Abstract

The high numbers of COVID-19 cases and deaths in Brazil have made Latin America an epicentre of the pandemic. SARS-CoV-2 established sustained transmission in Brazil early in the pandemic, but important gaps remain in our understanding of virus transmission dynamics at a national scale. We use 17,135 near-complete genomes sampled from 27 Brazilian states and bordering country Paraguay. From March to November 2020, we detected co-circulation of multiple viral lineages that were linked to multiple importations (predominantly from Europe). After November 2020, we detected large, local transmission clusters within the country. In the absence of effective restriction measures, the epidemic progressed, and in January 2021 there was emergence and onward spread, both within and abroad, of variants of concern and variants under monitoring, including Gamma (P.1) and Zeta (P.2). We also characterized a genomic overview of the epidemic in Paraguay and detected evidence of importation of SARS-CoV-2 ancestor lineages and variants of concern from Brazil. Our findings show that genomic surveillance in Brazil enabled assessment of the real-time spread of emerging SARS-CoV-2 variants.

Fig. 1. Key events after the first confirmed SARS-CoV-2 infection in Brazil.

a, Timeline of SARS-CoV-2 key events in Brazil. b, Epidemic curve showing the progression of reported daily viral infection numbers in Brazil from the beginning of the epidemic (grey) and deaths (red) in the same period, with restriction phases indicated by the horizontal bar at the bottom. c, Map of cumulative SARS-CoV-2 cases per 100,000 inhabitants in Brazil up to June 2021.

Fig. 2. Phylogenetic analysis and SARS-CoV-2 lineage dynamics in Brazil.

a, Map of Brazil with the number of sequences in GISAID as of 30 June 2021. The map is coloured according to geographical macro region: North (red), Northeast (green), Southeast (purple), Midwest (light blue) and South (light orange). AC, Acre; AL, Alagoas; AP, Amapá; AM, Amazonas; BA, Bahia; CE, Ceará; DF, Distrito Federal; ES, Espírito Santo; GO, Goiás; MA, Maranhão; MT, Mato Grosso; MS, Mato Grosso do Sul; MG, Minas Gerais; PA, Pará; PB, Paraíba; PR, Paraná; PE, Pernambuco; PI, Piauí; RR, Roraima; RO, Rondônia; RJ, Rio de Janeiro; RN, Rio Grande do Norte; RS, Rio Grande do Sul; SC, Santa Catarina; SP, São Paulo; SE Sergipe; TO, Tocantins. b, Temporal sampling of sequences in Brazilian states through time with VOCs highlighted and annotated according to their PANGO lineage assignment. c, Time-resolved maximum-likelihood phylogeny containing high-quality near-full genome sequences from Brazil (n = 3,866) obtained from this study, analysed against a backdrop of global reference sequences (n = 25,288). VUMs and VOCs are highlighted on the phylogeny. d, Sources of viral introductions into Brazil characterized as external introductions from the rest of the world. e, Sources of viral exchanges (imports and exports) into and out of Brazil. f, Number of viral exchanges within Brazilian regions by counting the state changes from the root to the tips of the phylogeny in c.

Fig. 3. Fully annotated Brazilian SARS-CoV-2 time tree.

Time-resolved maximum-likelihood phylogeny containing 17,135 high-quality Brazilian SARS-CoV-2 near-full-genome sequences (n = 3,866 generated in this study) analysed against a backdrop of global reference sequences. VUMs and VOCs are highlighted.

Fig. 4. Spatiotemporal spread of VOCs and VUMs in Brazil.

a, Phylogeographic reconstruction of the spread of the Gamma VOC in Brazil. Circles represent nodes of the maximum clade credibility phylogeny and are coloured according to their inferred time of occurrence. Shaded areas represent the 80% highest posterior density interval and depict the uncertainty of the phylogeographic estimates for each node. Solid curved lines denote the links between nodes and the directionality of movement. Differences in population density are shown on a dark-white scale. b, Phylogeographic reconstruction of the spread of the Zeta VUM across Brazil. Circles represent nodes of the maximum clade credibility phylogeny and are coloured according to their inferred time of occurrence. Shaded areas represent the 80% highest posterior density interval and depict the uncertainty of the phylogeographic estimates for each node. Solid curved lines denote the links between nodes and the directionality of movement. Differences in population density are shown on a dark-white scale. c, Number of exchanges of the Gamma variant between Brazilian regions (N, North; NE, Northeast; MD, Midwest; SE, Southeast; S, South). d, Number of exchanges of the Zeta variant between Brazilian regions. e, Sources of viral export of the VOC and VUM from Brazil to the rest of the world.

Fig. 5. The SARS-CoV-2 epidemic in Paraguay.

a, Epidemic curve showing the progression of reported viral infection numbers in Paraguay from the beginning of the epidemic (grey) and deaths (red) in the same period. b, Progressive distribution of the top 20 PANGO lineages in Paraguay over time. c, Time-resolved maximum-likelihood tree containing high-quality near-complete genome sequences from Paraguay (n = 63) obtained in this study, analysed against a backdrop of global reference sequences. VUMs and VOCs are highlighted on the phylogeny. Genome sequences from Paraguay obtained in this study are highlighted with red borders.

Fig. 6

Number of total cases plotted against the number of sequences available for each Brazilian state/region.