Epidemiological Surveillance Reveals the Rise and Establishment of the Omicron SARS-CoV-2 Variant in Brazil

Abstract

The introduction of SARS-CoV-2 variants of concern (VOCs) in Brazil has been associated with major impacts on the epidemiological and public health scenario. In this study, 291,571 samples were investigated for SARS-CoV-2 variants from August 2021 to March 2022 (the highest peak of positive cases) in four geographical regions of Brazil. To identify the frequency, introduction, and dispersion of SARS-CoV-2 variants in 12 Brazilian capitals, VOCs defining spike mutations were identified in 35,735 samples through genotyping and viral genome sequencing. Omicron VOC was detected in late November 2021 and replaced the Delta VOC in approximately 3.5 weeks. We estimated viral load differences between SARS-CoV-2 Delta and Omicron through the evaluation of the RT-qPCR cycle threshold (Ct) score in 77,262 samples. The analysis demonstrated that the Omicron VOC has a lower viral load in infected patients than the Delta VOC. Analyses of clinical outcomes in 17,586 patients across the country indicated that individuals infected with Omicron were less likely to need ventilatory support. The results of our study reinforce the importance of surveillance programs at the national level and showed the introduction and faster dispersion of Omicron over Delta VOC in Brazil without increasing the numbers of severe cases of COVID-19.

Epidemiology of the SARS-CoV-2 Omicron Variant Emergence in the Southeast Brazilian Population

“…According to our results, this increase in infected individuals was directly related to the introduction of the Omicron variant in this region, since the phylogenetic analysis revealed that 76% and 22% of the SARS-CoV-2 genomes evaluated in this period were classified as BA.1 and BA.1.1, respectively. Other studies corroborate our finding, showing that the arrival of the Omicron VOC caused an important change in the epidemiological scenario, culminating in the replacement of the Delta variant by Omicron in approximately 3.5 weeks, and reached a dominant plateau in different Brazilian capitals [26]. Furthermore, one of the relevant features of the Omicron variant is its ability to cause reinfection.…”

The Impact of SARS-CoV-2 Infection on the Length of Stay in the Neuro-ICU:A Prospective Multicenter Cohort Study in Eight Neuro-ICU, China Between February and April 2023

“… 14 Despite the relatively high vaccination rates, most countries have experienced a surge in COVID-19 cases after reducing lockdown measures, particularly in densely populated cities. 15 Because of the flexible public healthcare provision in China, the lifting of the COVID-19 lockdown measures in early 2023 did not result in significant overcrowding of medical resources. 16 This finding is consistent with our ICU mortality rate of 6.1% and an LOS of 5.2 days.…”