key: cord-1030967-r6boqj2k
authors: Del Brutto, Oscar H; Costa, Aldo F; Mera, Robertino M; Recalde, Bettsy Y; Bustos, Javier A; García, Héctor H
title: SARS-CoV-2 in rural Latin America. A population-based study in coastal Ecuador
date: 2020-07-27
journal: Clin Infect Dis
DOI: 10.1093/cid/ciaa1055
sha: 507d27c1f85934fe519790c49f063818b248e0f4
doc_id: 1030967
cord_uid: r6boqj2k

Antibodies to SARS-CoV-2 were detected in 303/673 rural Ecuadorian adults (45%), 77% of whom had compatible clinical manifestations. Seropositivity was associated with the use of open latrines. Our findings support the fears of mass spread of SARS-CoV-2 in rural Latin America and cannot exclude a contributing role for fecal-oral transmission.

The Atahualpa Project is a population-based prospective cohort studying individuals aged ≥40 years in rural Ecuador, starting on 2012 [4] . An abrupt increase of deaths in the village was noticed in April and May, 2020 (overall mortality rate: 21.6‰ population, almost threequarters of it attributable to SARS-CoV-2, configuring a 266% of excess mortality), that coincided with the peak of this pandemic in Ecuador, suggesting an outbreak of SARS-CoV-2 infection. Taking the opportunity of the above-mentioned well-established cohort, we assessed the prevalence, distribution, and risk factors associated with SARS-CoV-2 seropositivity in middle-aged and older adults living in this closed population.

Atahualpa is located in Coastal Ecuador. The village has electricity and almost all houses have piped water. A sizable proportion of houses do not have flushing toilet systems and still use open latrines. Inhabitants are homogeneous regarding race/ethnicity (Amerindian ancestry), lifestyles, and diet. Almost all men belong to the blue-collar class (artisan carpenters) and most women are homemakers. Atahualpa has a low index of migration and the adherence of the population to the Atahualpa Project has been high, which makes it an optimal setting for conducting population-based studies [5] .

For the present study, field personnel (including medical doctors) visited all houses of Atahualpa Project participants. Demographic data and risk factors were updated during house A c c e p t e d M a n u s c r i p t 4 visits. Individuals were examined to assess current or past (prior two months) clinical manifestations suggestive of COVID-19 disease, according to the recommendations of the World Health Organization [6] . Detection of SARS-CoV-2 IgM and IgG antibodies was performed using a lateral flow antibody test (BIOHIT Health Care Ltd., Cheshire, UK) in finger prick blood samples. The manufacturer reports 97.5% sensitivity with 99.5% specificity for IgM, and 97.5% sensitivity with 100% specificity for IgG detection of this kit.

Results of those tests were independently reviewed by two readers, with excellent Kappa coefficients for interrater agreement (0.91). Discrepancies were resolved by consensus. The study followed the standards for reporting of observational studies in epidemiology (STROBE) guidelines [7] , and the Independent Review Board of Universidad Espiritu Santo (IORG: 0010320; FWA: 00028878) approved the study protocol and informed consent forms.

Covariates were selected if they have been suggested to play a role in disease acquisition or spread, or in the development of clinical manifestations, and included age, gender, level of education, alcohol intake, number of individuals living in the house, number of bedrooms, having an open latrine, home confinement during the past two months, and cardiovascular health status, according to the American Heart Association criteria (smoking status, diet, physical activity, body mass index, blood pressure, fasting glucose, and total cholesterol blood levels) [8] .

Data analyses were carried out by using STATA version 16 (College Station, TX, USA). In univariate analyses, continuous variables were compared by linear models and categorical variables by the x 2 or Fisher exact test as appropriate. Mixed logistic regression models, where subjects were clustered within blocks, and each block was considered a panel of random intercept, were fitted using seropositivity to SARS-CoV-2 antibodies as the dependent variable, adjusted for the above-mentioned covariates. 

This study demonstrates a high (45%) seroprevalence to SARS-CoV-2, disseminated across the entire village, confirming fears of mass spread of the disease in rural populations of Latin America [9] . Despite almost nil migration into Atahualpa, many men travel to neighboring towns to trade the furniture they build as artisan carpenters. Atahualpa's scenario is typical of closed populations where inhabitants are immunologically naïve to a rapidly spreading pathogen. Rural populations of Latin America are additionally burdened by poor social determinants of health and inadequate access to medical care, and do not seem to be prepared for this pandemic at all [3] .

Most available data about COVID-19-related predisposing factors derives from clinical series in health centers, with only few urban community surveys covering sampling proportions of the target population [10, 11] . There are no similar community-wide studies reported from remote rural settings. In these settings, living conditions, risk factors and access to health care, are totally different than those in urban centers or in developed countries. A c c e p t e d M a n u s c r i p t 7 confinement to home was inversely associated with seropositivity. A multivariate model confirmed the associations of seropositivity with clinical manifestations and the use of latrines. We cannot conclude that presence of asymptomatic seropositive patients points to true asymptomatic cases. This was a cross-sectional survey, and both recall bias and the occurrence of other infections, could have contributed to it. Also, higher rates of asymptomatic infections than in our study were reported in Veneto, Italy [10] . Likewise, a Swiss study found a seroprevalence of about 11% after five weeks of the first demonstrated case, with most individuals being asymptomatic [11] .

On the basis of the demonstration of SARS-CoV-2 in feces [12] , it has been suggested that the fecal-oral route may contribute to the transmission of this pathogen in rural areas of the developing world [3] . The present study provides indirect support to the above-mentioned 

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