[COVID 19 infection: age-stratified population-based cohort seroepidemiological study in Asunción and Central]. / Infección por COVID 19: estudio seroepidemiológico de cohorte de base poblacional, estratificado por edad, en Asunción y Central.

BACKGROUND: COVID-19, caused by the severe acute respiratory syndrome virus type-2 (SARS-CoV-2), was declared a pandemic in March 2020. Seroprevalence studies are useful to estimate the proportion of the population previously infected, quantify the magnitude of transmission, estimate the fatality rate, evaluate the effect of interventions, and estimate the degree of immunity of the population. AIM: To determine the extension of the infection and the cumulative incidence of age-specific infection, determined by seropositivity in the population of the sanitary regions of Asunción and the Central Department of Paraguay. METHODS: Population-based cohort study. In Asunción 126 households and in the Central Department 609 were surveyed between December 2020 to March 2021. Three visits were made to the selected households. RESULTS: The testing rate was 66.6%, 1,699 people (324 in Asunción and 1,375 in Central) of the 2,553 people registered. In the first, second and third rounds, seroprevalences were 15.5%, 15.4% and 14.3% in Asunción, respectively; in Central 23.1%, 27.8% and 26.9%, respectively. There was a seroconversion between the first and second rounds of 5.9%, and in the third round 6.5%; the accumulated global seroprevalence was 26.9% (95% CI: 24.8-19.1); in Asunción 23.1% (95% CI: 18.9-28.0) and in Central 27.8% (95% CI: 25.5-30.2). 8.5% of the participants reported symptoms; of them, 54.2% had positive serology. CONCLUSION: The sero-prevalence was high with a low proportion of people with symptoms.

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

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.