Introduction

Since China began communicating deaths due to an unknown pneumonia in late December 2019, an outbreak of a new virus identified as SARS-CoV-2 has been in course. On March 16th, the first death by COVID-19 was reported in Brazil. Currently (July 23th), 82.890 official deaths and 2.231.871 confirmed SARS-CoV-2 infections were reported (Worldometer, 2020). Brazil has 211 million inhabitants, corresponding to 2.7% of the world population. However, more than 13 % of worldwide COVID-19 cases and deaths are concentrated in Brazil. Almost half (45%) of the officially reported COVID-19 deaths are concentrated in the southeast region of Brazil, mainly in the states of São Paulo and Rio de Janeiro. Minas Gerais is the largest southeast state, located in the richest Brazilian region, with high connectivity by roads to other states and a large flux of goods and persons. It has an extension of 586.528 km2and 21 million people on average, similar to Ukraine, France, and Spain. Nevertheless, according to official sources, it accumulates less than 2.170 deaths (SUS, 2020). The aforementioned state plays an important role due to its agribusiness and mining industry impacting strongly on the national economy under a pandemic scenario, leading to cost lives and business decrease. Test coverage is 5.45 tests per 1000 inhabitants (considering serological and PCR tests), the second smallest among Brazilian states (Ariadne, 2020). The social distancing percentage in Minas Gerais dropped from about 53% in the last week of March to around 38% in the second week of July (InLoco, 2020). In a scenario of a large population, intense human fluxes, and decrease in social distancing, the low coverage of COVID-19 testing represents the jeopardy of such striking underestimated deaths reported by governmental sources.
As the number of COVID-19 patients is increasing dramatically (Han et al., 2020), it is crucial to triage and evaluate confirmed infected/death cases. There is evidence suggesting that infected but asymptomatic people are still able to infect others (Day, 2020) and SARS-CoV-2 transmission from these cases has already been observed (Rothe et al., 2020; Tong et al., 2020). Likewise, superspreading events (SSEs), which are associated with both explosive growths early in an outbreak and sustained transmission in later stages have been reported (Frieden and Lee, 2020), leading to higher mortality. Simulation makes available rapid estimation of the infections course, providing quantification and understanding of the spatiotemporal outbreak spreading (Siettos and Russo, 2013). In this context, correct assessments of cases in a target population, as well as the trend of infections/deaths provide important insights which might guide authorities when making decisions (Nishiura et al., 2020).
Public data from the Registry Office (RO) (Cartorio, 2020) have pointed out 1.654 excess deaths due to SARS and COVID-19 in 2020 in Minas Gerais compared to the same period in 2019 (January 1st to July 1st). It represents 115 % of the COVID-19 official deaths informed by the State Surveillance Service, indicating potential excess deaths attributable to sub-notified COVID-19 deaths. The standard approach to calculate the expected number of deaths, in the absence of a given event of interest, uses the previous year’s historical all-deaths data for the same timeline as baseline reference (Nogueira et al., 2005). However, current social distancing and isolation are not comparable with any historical mortality rate reported so far, and therefore this approach does not reflect the expected excess mortality presently observed. The aim of this study was to analyse and consider other criteria for better estimating deaths, infected cases, and high mortality due to COVID-19, comparing its geographic distribution as well as its impact in different ethnic groups in Minas Gerais.