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Epidemiological Update: Increase of the Delta variant and its potential impact in the Region of the Americas, 8 August 2021

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In view of the increased circulation of the variant of concern (VOC) Delta in several countries within and outside the Region of the Americas, which in some areas is accompanied by an increase in hospitalizations, the Pan-American Health Organization / World Health Organization (PAHO / WHO) recommends reviewing preparedness plans and preparing for a possible increase in hospitalizations


Since the initial identification of SARS-CoV-2, as of 5 August 2021, more than 2.6 million complete genomic sequences have been shared worldwide, providing visibility and public access to this information. The ability to monitor viral evolution, almost in real time, has a direct impact on the public health response to the COVID-19 pandemic, as it allows the identification of changes in epidemiological patterns, changes in virulence, or even a decrease in the preventive efficacy of vaccines, among other contributions.

Globally, several countries with an increase in cases and hospitalizations with the emergence of Variant of Concern (VOC) Delta can be observed (Figure 1), including Member States in the Americas with high vaccination coverage. With the VOC Gamma as the predominant variant in several countries and territories of the Americas, and the emergence of the identification of VOC Delta in these same countries and territories, in addition to other variants of interest (VOI) (Figure 2), such as Lambda, for example, exhorts the necessity to point out to the Member States of the region the importance of the preparatory process for the expansion of care capacity in the face of a potential increase in cases, hospitalizations, and deaths.

In July 2020, variant B.1.617.2 was first reported, which was subsequently designated as VOC Delta, with significant health damage, however, over 13 months later, it has been reported by 135 countries globally and 24 countries and territories in the Americas Region. It is worth noting that since April 2021, a global exponential increase in VOC Delta samples has been observed. In July 2021, a global predominance of VOC Delta was observed in almost 90% of the samples worldwide (Figure 3). Such predominance remains even after considering VOI in the analysis (Figure 4).

Admittedly, this information regarding the variants must be evaluated with caution due to the possible biased representation of SARS-CoV-2 genomic sequencing data (GSD), with a higher contribution from high-income countries.

This bias should be considered when evaluating the graphs presented in this epidemiological update on the presence or absence of a particular variant in a location and its relative frequency. The presence of a variant does not necessarily mean its circulation in the community as it may be sporadic or travel-associated cases. In addition, not all countries share their data through the GISAID platform, and genetic sequencing capacity may differ from one country to another, which may explain the silence in signaling VOC or VOI circulating in their territories, and therefore negatively influence the ability to structure the system in its healthcare response.