On January 30, 2020, the World Health Organization (WHO) declared a pandemic due to discovering a new type of coronavirus in China (1). So far, more than 650 million individuals have been infected by the severe acute respiratory syndrome virus 2 (SARS-CoV-2), causing more than 6.6 million deaths. Like several countries, Brazil’s health system has been overwhelmed by the pandemic. The country’s economic inequality has also exacerbated the impact of the pandemic on vulnerable populations (2, 3). Regarding total cases and deaths, Brazil has been one of the countries most affected by COVID-19. Until March 2023, Brazil had recorded over 37 million patients and more than 699,000 deaths, making it the second-highest number of COVID-19 deaths worldwide. At the study period, according to data from the Brazilian Ministry of Health, during the period from August 2020 to October 2020, Brazil had a significant increase in the number of COVID-19 cases and deaths as follows: August 2020: 3,669,995 confirmed cases and 118,649 deaths, September 2020: 4,847,092 confirmed cases and 143,962 deaths, October 2020: 5,394,128 confirmed cases and 157,981 deaths (4–7).

Critically, there are several economically disadvantaged communities in Brazil, especially those living in a situation of social vulnerability, such as the quilombola settlements in Brazil (2). Quilombola communities comprise ethnic-racial groups of black and African ancestry brought to Brazil and enslaved between the 16th and 19th centuries (3). After the abolition of slavery, communities emerged with their own sociocultural, economic, and religious characteristics that contributed to maintaining the particular ways of life within the quilombola communities and consolidating their territories (4, 5). There are 2,958 quilombola communities in Brazil certified by the Palmares Cultural Foundation, 35 of which are located in Sergipe (6–8). Despite globalization and modernization, these quilombola communities still have low socioeconomic and health conditions, with insufficient access to the healthcare system. Consequently, the quilombola communities are more vulnerable and susceptible to chronic diseases, such as systemic arterial hypertension (9–11), diabetes (12), and obesity (13), that, when associated with SARS-CoV-2, can result in a high mortality rate (9, 14).

The historic social vulnerability of quilombola communities has been a concern during the COVID-19 pandemic, a period also marked by the local political failure to implement fully adequate public protection policies (15, 16). For instance, quilombola communities still suffer from inadequate access to water and other basic infrastructure necessary for maintaining hygiene conditions, which are required to prevent the spread of the SARS-CoV-2 virus (17, 18). It is essential to mention that the World Health Organization (WHO) on 22 May 2020 declared Latin America as an epicenter of the coronavirus pandemic (19). Since there are several vulnerable areas in Latin America, it is necessary to sufficiently characterize the serological status and the circulation of SARS-CoV-2 in vulnerable communities of this local, as previously performed in Peru (20).

Notably, social vulnerability is primarily the case of rural areas of North and Northeast Brazil, where several quilombola communities live. In these regions, there was an inefficient implementation of the National Policy for Total Health for the Black Population (PNSIPN), which was created in 2009 (14, 21) inappropriate application of Law 14.021/21 that fundament the Emergency Plan to Combat COVID-19 for vulnerable communities, including Indians and Quilombolas (15, 17). The National Coordination for the Articulation of Black Rural Quilombola Communities in Brazil (CONAQ), in partnership with the Instituto Socio Ambiental, has launched a digital platform entitled “Observatório da COVID-19 nos Quilombos” to provide information on the number of COVID-19 cases (10). According to this platform, by January 12, 2022, there were 5,666 confirmed COVID-19 cases and 301 deaths in quilombola communitie (17). However, the serological status and the circulation of SARS-CoV-2 among quilombola communities and their relationship with the presence of risk factors or preexisting chronic diseases in the quilombola communities were not investigated so far (4–7). Thus, this study was performed to address this issue.

This cross-sectional study characterizes the SARS-COV-2 infection profile in quilombola communities in Brazil, which are under social vulnerability, representing an issue of concern highly associated with high infection rates during the COVID-19 pandemic (8). In agreement, we found that there is a higher percentage of SARS-COV-2 reactivity in quilombola communities than in the population of Sergipe. Typical COVID-19-related symptoms (e.g., muscle pain, headache, anosmia, and ageusia (loss of taste) were frequently demonstrated by IgM- or IgG-positive (reagent) individuals. Furthermore, most individuals affected by COVID-19 were female, which is in agreement with previous findings by Borges et al. (17) and Gonçalves et al. (8). However, we cannot conclude that this result means that females are more affected than males in these populations because, in addition to the selection bias in the study participants (>3 females/1 male), Sergipe is a state with a higher number of females (about 51.74%) to male population (with 48,26%) (36). To the best of our knowledge, this work characterizes for the first time the association between sociodemographic or risk factors and chronic diseases with the SARS-CoV-2 infection profile (symptoms and comorbidities) of individuals from the quilombola communities.

This study highlights the importance of precise COVID-19 diagnosis, neglected in quilombola communities, despite being essential for individuals’ health and social care to delay SARS-CoV-2 transmission. This is highly important since there was a higher incidence of SARS-CoV-2 infection in the quilombola communities compared to the general Sergipe population. In this context, specific IgM antibodies for SARS-CoV-2 can be detected approximately 3–5 days after the onset of infection, and 14.6% of the individuals from the quilombola communities were IgM-positive. Nonetheless, although they were acutely infected, they lived in free contact with the other 85.4% of uninfected individuals in these communities. Furthermore, the indices of IgG-positive individuals indicated that 16.7% of the quilombola populations were with late, secondary, or previous SARS-CoV-2 infection. Despite that, the individuals who participated in our study were followed up by municipal health departments. No adverse outcomes (disease worsening, resulting hospitalization or death) were reported 12 months after testing.

Although a systematic review and meta-analysis of the SARS-CoV-2 seroprevalence worldwide revealed that the SARS-CoV-2 seroprevalence varied markedly among geographic regions (37), our data is following the epidemiological studies in Africa showing a lower incidence of severe COVID-19 than in developed countries (38). However, although there are different hypotheses to explain these better outcomes in Africa compared to other continents, it remains undetermined. Therefore, future studies are essential to investigate the relationship between the hygiene hypothesis, the COVID-19 pandemic, and the human microbiome in the epidemiology of SARS-CoV-2 infections (39). These better outcomes in low-income areas are even more surprising because comorbidities representing risk factors for severe COVID-19, such as arterial hypertension and diabetes (40), were highly presented in our study cohort and frequently reported in quilombola communities (9). Of note, a 26% prevalence of arterial hypertension is reported in the quilombola communities of Sergipe, which is higher than the standard observed in the general population (20.4%) in the same state (9). Likewise, we also observed the incidence of diabetes (DM) in the population tested, as reported by Roriz et al. (41) in patients from a hospital in the state of Sergipe, and the indication of hyperglycemia, which may be related to the risk of developing metabolic syndrome and has already been observed predominantly in quilombola women (42). Despite that, most IgM and IgG seropositive cases were asymptomatic (79.9%), as Borges et al. (43) observed in the general population.

Among symptomatic patients, headache was the most common complaint in our study, in accordance with a previous report showing that headache is a symptom often associated with COVID-19, requiring clinical attention because it can persist beyond the acute disease phase as a persistent symptom (44). Furthermore, we also observed the presence of cough in seropositive individuals (4.8%), as found by Adil et al. (45) and Yang et al. (46), with cough being the second most frequent symptom reported by these authors. In addition, some studies considered coughing to be a trigger for headaches, which may explain the higher incidence of both symptoms in the population tested (44). Although we found rhinitis o be the third most frequent symptom (4.4%), there are few reports of patients with this symptom in the literature (47, 48). We also found the loss of smell and taste frequently reported in our cohort, which are hallmark symptoms of COVID-19 (49). We saw similar symptoms and comorbidities in the SARS-CoV-2 positive and negative groups. This fact might be explained by the cocirculation of SARS-CoV-2 and other respiratory viruses, such as influenza viruses, respiratory syncytial virus, or adenoviruses, enhancing the respiratory disease burden worldwide and causing overlapping symptoms in SARS-CoV-2 positive and negative individuals (50, 51).

Despite being relevant to characterize the clinical profile and the high number of SARS-COV-2 infections in quilombola communities, this study has limitations. We could have used more accurate tests (e.g., RT-PCR) to evaluate our study cohort’s reactivity and serological status. However, the anti-SARS-CoV-2 IgM and IgG antibodies were tested using an approved approach by the Brazilian Health Regulatory Agency (ANVISA; Registration number: 814647500072) and approved by the FDA (31). This test has been used frequently in our studies (26) and qualitatively detects IgM and IgG antibodies separately with a sensitivity of 96.8% and specificity of 96.52% (52, 53). Another limitation of our study is that we performed a cross-sectional study. Thus, we do not follow the epidemiological dynamics of SARS-CoV-2 infections during the COVID-19 pandemic in the quilombola communities. Another limitation is that despite not representing a comprehensive epidemiological analysis, this study is an investigation of social importance in under-tested people, acting as an instrument for understanding the pandemic in these communities.

In conclusion, there was a higher number of SARS-COV-2 infections in quilombola communities than in the local population in Brazil when we developed this study. Testing for the SARS-CoV-2 infectious status could have played a significant role in the transmission of this virus across the quilombola populations, particularly during the pandemic when vaccines were unavailable. However, this population presented favorable disease outcomes. Thus, political initiatives developed by the current study should be supported by local governments and broadly implemented through public policy to mitigate the damage to quilombola populations during future pandemics or epidemic events.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding authors.

The studies involving human participants were reviewed and approved by Ethics Committee of the Federal University of Sergipe (CAAE 48254821.3.0000.554 and date 01/11/2021). The patients/participants provided their written informed consent to participate in this study.

AM, LB, DS, JR, AS, GI, IM, KS, PJ, FS, FA, SM, BO, IC, and OM: conceptualization and methodology. FV, DF, LS, SS, RG, and BP: figures and tables. CF, BP, CB, SS, RG, LB, BM, and OM: writing—preparation of the original draft. BP, CF, AM, LB, CB, FV, DF, LS, OM, and BM: writing—proofreading and editing. All authors contributed to the article and approved the submitted version.

This work was supported by CAPES (finance code 001) to FV; the National Council for Scientific and Technological Development (CNPq), Brazil (grants: 309482/2022-4 to OM and 102430/2022-5 to LS); Federal University of Ouro Preto (grant number 23109.000928/2020-33); São Paulo Research Foundation (FAPESP grant 2018/18886-9 to OM and 2020/16246-2 to DF).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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