The challenges of COVID-19 in the Brazilian Amazonian communities and the importance of seroepidemiological surveillance studies

The emergence of a new Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Wuhan, China, in late 2019, coupled with its rapid spread to Chinese provinces and to more than 100 countries on all continents, has led the World Health Organization (WHO) to define the situation as a new pandemic [1]. The rapid spread of SARS-CoV-2 has forced all nations in the world to mobilize a variety of efforts to restrain the spread of the virus, such as: (i) put in place strong measures to detect disease early, (ii) isolate and treat cases, (iii) trace contacts, (iv) promote social distancing measures commensurate with the risk, (v) conducting studies on the severity and transmissibility of the virus, (vi) increase in the hospital network, especially in the number of intensive care beds exclusively for patients with COVID-19, and (vii) sharing data and biological material [1]; however, given the many uncertainties regarding the transmissibility, pathogenicity and virulence of this new infectious agent, the effectiveness of these efforts is still unknown. SARS-CoV-2 is the seventh coronavirus known to infect human beings (HCoVs - Human Coronavirus); SARS-CoV (Severe Acute Respiratory Syndrome Coronavirus), MERS-CoV (Middle East Respiratory Syndrome Coronavirus) and SARS-CoV-2 can cause serious diseases, while HCoV-HKU1, HCoV-NL63, HCoV-OC43 and HCoV-229E are strains associated with mild symptoms [2].

Worldwide, the diagnosis of SARS-CoV-2 infection is mainly based on moderate and severe symptomatic cases requiring hospitalization. Asymptomatic cases, which are undocumented, represents a critical epidemiological feature in the modulation of the potential spread of an emerging respiratory virus such as SARS-CoV-2 [3]. These infections go unnoticed and, depending on their capacity for transmissibility and contagion, can expose a much larger portion of the population to the virus than would normally occur [3]. The current situation of the pandemic exceeds five million cases and 340 thousand deaths, with a mortality rate of approximately 5%; however, these figures are underestimates [4], mainly due to asymptomatic cases, the lack of mass testing, the lack of testing for suspicious deaths and the collapse of the health system, which inflates the mortality rate. From an epidemiological point of view, little is still known about SARS-CoV-2, and it is extremely difficult to compare this virus to human coronaviruses that cause mild and moderate disease or to those that are highly pathogenic and virulent, such as SARS-CoV and MERS-CoV [5, 6].

The coronavirus pandemic’s life-altering effects are likely to result in lasting physical and mental health consequences for many people, particularly those from vulnerable populations. In this sense, the extent and significance of the present epidemic in the Brazilian Amazon is in need of investigation.

Since the elimination of beta-coronavirus circulation requires a minimum herd immunity (indications 50–66%) [7], the information for which is still unknown at the local, national or global levels, conducting seroepidemiological and surveillance studies on SARS-CoV-2 in geographic areas such as the Amazon is extremely important, as it will allow for the assessment of the prevalence and titre of antibodies anti-SARS-CoV-2, mortality and case fatality rates and the epidemiological aspects of risk of exposure in communities from different population strata, such as riberinhos (riverain communities), quilombola (Afro-descendant communities) and indigenous peoples, providing an improvement in the decision-making of future epidemics.

It is important to note that recent study indicates that antibody response offered after infection with the SARC-CoV-2 may not be long enough [8]. If it can be influenced by type of serological assay, is still uncertain; but certainly it could impact the interpretation of seroepidemiological data, as well as, the level of exposure of the population to a second wave of infection. Thus, aiming to avoid bias, we propose that seroepidemiological studies should use methods with high sensibility and specificity, as enzyme-linked immunosorbent assay (ELISA) and immunometric quimioluminescence essay, in order to minimize any interference on antibody prevalence calculation. Furthermore, follow-up assessments of individuals in the population could tell us what is the average time of presence of antibodies in the blood and, thus, estimate the level of susceptibility to a new possible epidemic wave.

Seroepidemiological study associated with the sociocultural understanding of the different Amazonian indigenous communities will indicate the current level of individual susceptibility that may sustain a second wave of the epidemic and who should be the target for future vaccines. It is worth noting that comprehensive seroepidemiological information is expected to be provided, aiming the immediate use in decision-making and in the creation of government health policies. In addition to seroepidemiological surveillance studies, is paramount importance that the Brazilian government creates a detailed contingency plan that presents measures for the prevention and control of the epidemic in these communities, as well as supply the access to diagnosis, drinking water, hygiene material, emergency financial aid and Intensive Care Unit beds.