The Brazilian variant of the new coronavirus – known as P.1. or variant of Manaus – probably emerged in the Amazonian capital in mid-November 2020, about a month before the number of hospitalizations for severe acute respiratory syndrome in the city made a leap. In just seven weeks, P.1. became the most prevalent strain of Sars-CoV-2 in the region, report researchers from the Brazil-United Kingdom Center for Discovery, Diagnosis, Genomics and Epidemiology of Arbovirus (CADDE), in an article published on its website.
The conclusions of the group coordinated by Ester Sabino, from the University of São Paulo (USP), and Nuno Faria, from Oxford University (United Kingdom), are based on the genomic analysis of 184 samples of nasopharyngeal secretion from patients diagnosed with Covid-19 in a laboratory in Manaus between November 2020 and January 2021.
Through mathematical modeling, crossing genomic and mortality data, the CADDE team calculates that to P.1. between 1.4 and 2.2 times more transmissible than the versions that preceded it. Scientists also estimate that, in part of the individuals already infected with Sars-CoV-2 – somewhere between 25% and 61% -, the new variant can circumvent the immune system and cause a new infection. The modeling work was done in collaboration with researchers at Imperial College London (United Kingdom).
“These numbers are an approximation, because it is a model. Anyway, the message that the data sends is: even those who have had Covid-19 need to continue to be cautious. The new strain is more transmissible and can infect even those who already have antibodies against the coronavirus ”, says Ester, to Agência FAPESP. “This is what happened in Manaus. A good part of the population already had immunity and even then there was a great epidemic ”, he concludes.
The research was supported by FAPESP and is in the process of peer review. Another study recently released by researchers from the Oswaldo Cruz Foundation (Fiocruz) Amazônia indicates that, in individuals infected with P.1., The viral load in the body can be up to ten times higher.
In the CADDE article, the researchers report that, until February 24, 2021, this variant of Manaus had been detected in six Brazilian states. In all, they received 92 thousand air passengers from Manaus in November 2020. Of these, most of them had São Paulo as their destination (just over 30 thousand). Then came other cities in Amazonas, Pará, Rondônia, Ceará and Roraima. According to the authors, therefore, it is likely that there have been multiple introductions of the new variant in these locations.
Key coronavirus mutations
The sequencing of the viral genome of the 184 samples was done with a technology known as MinION, which, being portable and inexpensive, makes it possible to carry out studies that help to understand the process of evolution of the virus.
The researchers concluded that P.1. descends from strain B.1.128, which was first identified in Manaus in March 2020. When compared to the parent strain, the variant has 17 mutations, ten in the spike protein, used by the virus to bind to human cells and make viable the infection.
Three mutations are considered most important – the N501Y, the K417T and the E484K. According to Sabino, these three key mutations are identical to those found in the most transmissible variant reported in South Africa (B.1.351).
The variant of concern discovered in the United Kingdom (B.1.1.7.) Presents only the E484K mutation in the RBD region. For the authors, the data indicate that there was a convergent evolution process. That is, certain mutations that confer an advantage to the virus appeared in parallel in different geographic regions. By natural selection, these variants have been standing out from the strains previously prevalent in these locations.
“Until effective vaccines are available to everyone, non-pharmacological interventions [distanciamento social, uso de máscara e higiene das mãos] continue to be necessary and important to reduce the emergence of new variants ”, stress the CADDE researchers.