SARS-CoV-2 variants with concerning characteristics have emerged since the end of 2020. Surveillance of SARS-CoV-2 variants was performed on a total of 4,851 samples from the capital city and 10 provinces of Argentina, during 51 epidemiological weeks (EWs) that covered the end of the first wave and the ongoing second wave of the COVID-19 pandemic in the country (EW 44/2020 to EW 41/2021). The surveillance strategy was mainly based on Sanger sequencing of a Spike coding region that allows the identification of signature mutations associated with variants. In addition, whole-genome sequences were obtained from 637 samples. The main variants found were Gamma and Lambda, and to a lesser extent, Alpha, Zeta, and Epsilon, and more recently, Delta. Whereas, Gamma dominated in different regions of the country, both Gamma and Lambda prevailed in the most populated area, the metropolitan region of Buenos Aires. The lineages that circulated on the first wave were replaced by emergent variants in a term of a few weeks. At the end of the ongoing second wave, Delta began to be detected, replacing Gamma and Lambda. This scenario is consistent with the Latin American variant landscape, so far characterized by a concurrent increase in Delta circulation and a stabilization in the number of cases. The cost-effective surveillance protocol presented here allowed for a rapid response in a resource-limited setting, added information on the expansion of Lambda in South America, and contributed to the implementation of public health measures to control the disease spread in Argentina.

The second wave of COVID-19 occurred in South America in early 2021 and was mainly driven by Gamma and Lambda variants. In this study, we aimed to describe the emergence and local genomic diversity of the SARS-CoV-2 Lambda variant in Argentina, from its initial entry into the country until its detection ceased. Molecular surveillance was conducted on 9356 samples from Argentina between October 2020 and April 2022, and sequencing, phylogenetic, and phylogeographic analyses were performed. Our findings revealed that the Lambda variant was first detected in Argentina in January 2021 and steadily increased in frequency until it peaked in April 2021, with continued detection throughout the year. Phylodynamic analyses showed that at least 18 introductions of the Lambda variant into the country occurred, with nine of them having evidence of onward local transmission. The spatial–-temporal reconstruction showed that Argentine clades were associated with Lambda sequences from Latin America and suggested an initial diversification in the Metropolitan Area of Buenos Aires before spreading to other regions in Argentina. Genetic analyses of genome sequences allowed us to describe the mutational patterns of the Argentine Lambda sequences and detect the emergence of rare mutations in an immunocompromised patient. Our study highlights the importance of genomic surveillance in identifying the introduction and geographical distribution of the SARS-CoV-2 Lambda variant, as well as in monitoring the emergence of mutations that could be involved in the evolutionary leaps that characterize variants of concern.

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Background: Many patients with myotonic dystrophy type 1 (DM1) develop muscular atrophy and weakness accompanied with myotonia in their adulthood. Some patients with DM1 have cataracts and heart problems without muscular weakness. CTG expansion in 3' untranslated region of DMPK gene causes DM1. The detection of this mutation has been done using Southern blotting or PCR-Southern blotting. But these methods need many procedures. Recently, the triplet repeat primed PCR (TP-PCR) was developed to detect some nucleotides repeat expansions. Objective: We tried to apply this TP-PCR methods to detect the Japanese DM1 patients and aimed to evaluate the efficacy for screening DM1. Patients and methods: We took peripheral blood from 10 Japanese patients in our hospital with informed consent. Three of them had cataracts and abnormal ECG findings without muscular weakness. We designed primers and an anchor-primer according to the previous reports about TP-PCR for SCA36 and C9ORF72. We examined the TP-PCR and fragment analysis each with fluorescent-labeled primers by autosequencer, and did PCR-Southern blotting analysis. Results: The PCR-fragment analysis revealed mild expansion within 100 repeats in three patients without muscular weakness. Seven other patients had smear-like abnormal band in the PCR-Southern blotting. TP-PCR showed smear-like-peaks in all 10 patients including three mild ones. Conclusion: This method could detect all abnormal expansions. But above 100 repeats, all patients showed almost the same pattern and could not show the difference of the size of repeats. The triplet repeat primed PCR is a convenient and useful method for screening DM1.