High infection to SARS-CoV-2 in an indigen community of the Colombian Amazon region

Introduction. COVID-19 is a pathology caused by the SARS-CoV2 virus. The World Health Organization has reported more than 225 million cases and 4.5 million deaths worldwide. Objective: To describe the seroprevalence, spatial distribution, and clinical and sociodemographic variables of SARS-CoV2 in a community of the Colombian Amazon region. Methods. In December 2020, a cross-sectional observational study was carried out in a population located in the Colombian Amazon in the municipality of Mitú. Sociodemographic and clinical data were taken. Besides, 590 blood samples were taken, and an antibody detection was carried out with an ELISA and a recombinant protein N antigen of SARS-CoV2. Results. A seroprevalence of 57.6% was observed. The highest proportion of the infection is located in inter-municipal transport zones. The bivariate analysis did not show differences in the SARS-CoV2 infection rate concerning the variables sex, age-range, and the presence of comorbidities (P> 0.05). The bivariate and multivariate analysis showed that being symptomatic and presenting neurological manifestations of the upper respiratory tract are clinical variables associated with SARS-CoV2 infection (P <0.05). One of the causes of this virus's high spread in this community could be that 53.3% of the people were asymptomatic. Conclusions. Our data showed a high burden and transmission of SARSPreprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 17 September 2021 doi:10.20944/preprints202109.0307.v1


Introduction
The World Health Organization (WHO) has reported more than 225 million cases and 4.5 million deaths related to COVID-19 in the world (1). At present, in a short time, the clinical characteristics and environmental factors related to the spread of SARS-CoV-2 in the general population have been studied in depth (2). However, little is known about this infection in populations of indigenous descent.
Colombia is one of the largest populations with indigenous heritage, and some of them are found in the Amazon. More than 64 indigenous ethnic groups have been described, and 58% of the inhabitants of this region belong to or have a genetic ancestry related to one of these ancestral communities (3,4). On the other hand, these populations have certain cultural conceptions against this new virus, which would be linked to the little use of protection measures. Therefore, there would be a high proportion of asymptomatic individuals that would facilitate the spread of SARS-CoV-2. However, it is unknown in Colombia and neighboring countries such as Brazil, Peru, and Venezuela the behavior and spread of this virus in indigenous communities. This work's objective was to describe the seroprevalence, spatial distribution, and clinical and sociodemographic variables related to SARS-CoV2 infection in a population of indigenous ancestry from the municipality of Mitú, Vaupés, Colombian Amazon.

Methods.
Type of study, geographic location, and size of the sample. In December 2020, a crosssectional observational study was carried out. The study was carried out in the municipality of Mitú, department of Vaupés, a region that occupies part of the great Colombian Amazon (5). The department is located in the South East of Colombia on the border with Brazil ( Figure 1). Five hundred ninety people were included, the size of the sample was calculated based on the Mitú population of 16,580, with a reliability of 95% and a margin of error of 4% (EPIDAT 3.1). Spatial distribution of SARS-CoV2 in the municipality of Mitú. Analysis of the point map showed a distribution of cases throughout the municipality. However, the cases were mainly concentrated in areas close to the airport terminal ( Figure 1).

Figure 1. Spatial distribution through point map for SARS-CoV-2 infection in Mitú.
A distribution of SARS-CoV2 cases is observed throughout the municipality of Mitú, with relevant areas of concentration of those infected by SARS-CoV2 close to airport terminal.
Seropositivity for SARS-CoV2 and gender. No statistically significant differences were found between the percentage of infection between men and women (P> 0.05) (Table 2, Figure 2). However, a high proportion of infected was evidenced in both genders (> 55%).  There is no difference in seropositivity or OD of total antibodies against SARS-CoV2 between men and women. More than 50% of the data is well above the cut-off.
Relationship between seropositivity and age ranges. There were no differences between the percentage of SARS-CoV2 infection in the different age groups (P> 0.05) (Table 2, Figure 3). Except for the group ≥70 years, all the population groups presented seropositivity> 50%. Figure 3. Relationship between the age ranges evaluated against the serological data for SARS-CoV-2. No statistically significant differences were observed when comparing the kinetics of total antibodies against the different age groups.
Seropositivity and comorbidities. Between individuals with some comorbidity and those who do not, no statistically significant differences were found with seroprevalence. However, 50% of the individuals with comorbidities had been exposed to this new coronavirus (Table   3, Figure 4).  Figure 4 Relationship between having some comorbidity versus the serological data for SARS-CoV-2. No statistically significant differences were observed when comparing the total antibody kinetics between individuals with some comorbidity versus those who did not.
Seropositivity to SARS-CoV2 and history of clinical manifestations related to COVID19. Higher seroprevalence and elevated antibody titers against SARS-CoV2 were observed among individuals who had a history of pulmonary and extrapulmonary clinical manifestations in the last three months P <0.05) (Table 3, Figure 5). 53.3% of the asymptomatic individuals were seropositive. Variables that explain the seropositivity for SARS-CoV2 in the municipality of Mitú.

Discussion.
The seroprevalence against SARS-CoV2 evidenced in this area of the Colombian Amazon was 57.6% and could be considered within the seroprevalence studies as one of the world's highest. Our findings exceed those found in the principal city of the Brazilian Amazon, Manaus, where 44% community seroprevalence was reported (7), and the one made in Atahualpa Ecuador (8), with 45%. At the local level, this infection rate is comparable to that observed by us in the city of Montería, where we show high community immunity against this new virus (55%) (9).
The reasons that could explain this high seropositivity against SARS-CoV2 in the municipality of Mitu could be related to the typical cultural behaviors in these populations, such as sharing household utensils, having numerous family nuclei, and engaging in agricultural economic activities (10). Besides, Mitu is considered a small city of 16,580 inhabitants, and all these factors could influence the free circulation of SARS-CoV-2 and the high infection rate observed in this population. However, it is impossible to differentiate if these SARS-CoV-2 infections are active or an immunological trace of this infection since we evaluate total antibodies and not the active search for cases.
Regarding the spatial distribution of this infection, it was observed that the formal and informal trade zones and residential areas adjacent to inter-municipal transport zones were hotspots for SARS-CoV-2 infection in this population. These findings agree with Liu et al.
( (11), in which it was observed that in these areas, the spread of SARS-CoV-2 is favored, mainly if biosafety measures such as social distancing, use of masks, and handwashing are not applied.
Regarding the sex of the population evaluated, no differences were found in the SARS-CoV-2 infection rate. However, the high proportion of infected in both genders is striking, which is higher than 55% and reflects an essential spread of this virus in men and women of Mitú.
On the other hand, this finding makes us reconsider one of the paradigms of this disease: the greater susceptibility of SARS-CoV2 infection in males. Testosterone has been reported to promote androgen receptors at the nuclear level that facilitate the expression of TMPRSS2 receptors on the cell membrane, thereby promoting the entry of SARS-CoV2 into the host cell (12,13). The male hormone can induce a greater expression of ACE2 receptors at the cardiac and renal level, which is another receptor involved in this infection's pathogenesis (12). Therefore, it would be necessary to analyze this topic more carefully. In the indigenous population and other populations, we did not find evidence that the SARS-CoV-2 infection rate is affected by the sex variable (14).
Regarding the evaluated age ranges, we did not find differences between the percentage of infection with SARS-CoV-2. This finding is consistent with what was found in Sergipe in Brazil, where no differences were found in the seropositivity rate concerning age ranges (15).
However, the infection rate in these Brazilian age groups does not exceed 15%. While in the present study the population of indigenous ancestry, the infection rate is higher than 48%. It could be related to a higher infection rate in the ages 20-39 years (59.5%) because they are the predominantly productive age group. 60% of this population is engaged in informal economic activities (16), in which it is complicated to maintain self-care and isolation measures. Therefore, these infected individuals may have spread the virus to individuals of their family nuclei belonging to other age groups.
When comparing whether individuals with comorbidities presented greater seropositivity against SARS-CoV-2, it was not found that having hypertension or diabetes was related to an increase in the infection rate. However, it is essential to mention that suffering from comorbidities is related to greater severity and prevalence of complications such as acute respiratory distress syndrome, acute kidney injury, and septic shock (17).
The multivariate analysis showed that the presence of pulmonary and extrapulmonary symptoms of COVID-19 is the variable that best explains seropositivity against SARS-CoV-2 in an indigenous population. Furthermore, it was found that the clinical manifestations of the upper respiratory tract such as anosmia and ageusia are clinical variables that can be pathognomonic of SARS-CoV-2 infection in this population, and these findings have also been reported in the general population (17). However, it is important to note that 53.3% of asymptomatic individuals had antibodies against SARS-CoV-2. This could be one of the principal explanations for the high seropositivity and widespread SARS-CoV-2 in this population. However, the present study's serological and clinical findings would be circumscribed mainly by the dynamics of the SARS-CoV-2 infection in the Mitú population.
In other words, it is complex to extrapolate the data of this work with other indigenous communities of the Amazon, taking into account the ethnic plurality and genetics of these populations.
In conclusions, our data showed a high burden and transmission of SARS-CoV-2 in this indigenous community in 2020. Therefore, these findings show that is necessary to strengthen the sanitary services for future outbreaks that could be related to this coronavirus or other viruses. Finally, it is important to continue studying how this infection and other diseases compromise and impact the public health of these ancestry communities.