Confirmed First Year Expansion of COVID-19 Pandemic in Brazil
Authors: Celaschi Sergio 
Published: August 2022

Background: COVID-19 was first reported in Brazil in February 2020 – EPI week # 9. One semester latter, the country became one of the worst affected globally. After twelve months from the first reported case, the number of confirmed cases and deaths crossed 10 million and 248.5 thousand, respectively. Since the start of the epidemic in Brazil, several types of Non-pharmaceutical Interventions - NPI have been adopted with varied success. This work aims to confirm previous forecasts reported on September, 2020 for the expansion of the COVID-19 pandemic in Brazil, the most populated South American country with over 120 million inhabitants. Methods: The methodology employed in this work was presented in a previous publication. In such methodology, a first series of published data, determines the epidemiological parameters that govern the dynamics of the compartmental model, and adjust the model parameters aiming to forecast the COVID-19 evolutionary outbreak in a longer period. The deterministic and compartmental model provides predictions of the time series of infected individuals and fatalities in the studied population. A SEIR compartmental model was previously selected to estimate outcomes to the dynamics of the COVID-19 epidemic breakout in Brazil. This model takes into account two dominant lineages of the SARS-CoV-2, and a time-varying reproduction number R(t) to estimate the epidemic behavior. Compartments for individuals vaccinated, and newer prevalent SARS-Cov-2 variants were not included. A time-dependent incidence weight on R(t) accounted for Non Pharmaceutical Interventions (NPI). Results: The cohort study was set as a city population-based analysis. Population-based sample, 3,862,311 during the first study period, was the number of confirmed cases on infected individuals. A previous analysis, restricted to the city of S. Paulo - Brazil, was applied to predict the consequences of holding for posterior NPI releases, and indicates the appearance of a second wave starting last quarter of 2020. A second series of official data available from September 1st, 2020 to February 28, 2021, covering the whole Brazilian country, confirms the forecasts previously reported for the evolution of infected people and fatalities. Conclusion: This work quantifies the importance of the adopted and enforced Non-pharmaceutical Interventions - NPI to control the spread of the COVID-19 pandemic in Brazil, as predicted by a compartmental model. By February 28, 2021, the number of confirmed cases reached 10,551,259 - 5% bellow predicted average of accumulated cases, and fatalities accounted for 254,942 - 4% above accumulated average of estimated deaths. After March 1st, 2021 new peaks on reported numbers of daily new infected and new fatalities appeared and were label as the second wave. They resulted as a combination to the presence of the prevalent SARS-CoV-2 P1 variant, the progressive NPIs realise, and the increased number of vaccinated individuals. Regarding the original SARS-CoV-2 form and its variant, the only model assumption is their distinct incubation rates.