Resistant Escherichia coli isolated from wild mammals from two rescue and rehabilitation centers in Costa Rica: characterization and public health relevance.

This study aimed to characterize the antimicrobial resistance (AMR) and virulence profiles of 67 Escherichia coli isolates obtained from faecal samples of 77 wild mammals from 19 different species, admitted in two rescue and rehabilitation centers in Costa Rica. It was possible to classify 48% (n = 32) of the isolates as multidrug-resistant, and while the highest resistance levels were found towards commonly prescribed antimicrobials, resistance to fluoroquinolones and third generation cephalosporins were also observed. Isolates obtained from samples of rehabilitated animals or animals treated with antibiotics were found to have significantly higher AMR levels, with the former also having a significant association with a multidrug-resistance profile. Additionally, the isolates displayed the capacity to produce α-haemolysins (n = 64, 96%), biofilms (n = 51, 76%) and protease (n = 21, 31%). Our results showed that AMR might be a widespread phenomenon within Costa Rican wildlife and that both free-ranging and rehabilitated wild mammals are potential carriers of bacteria with important resistance and virulence profiles. These results highlight the need to study potential sources of resistance determinants to wildlife, and to determine if wild animals can disseminate resistant bacteria in the environment, potentially posing a significant threat to public health and hindering the implementation of a "One Health" approach.

Integrative taxonomy of Anaporrhutum mundae sp. nov. (Trematoda: Gorgoderidae), a parasite of the Munda round ray Urotrygon munda (Urotrygonidae) in Costa Rica.

A new species of trematode of anaporrhutine gorgoderid, from the gill chambers of the Munda round ray Urotrygon munda in Costa Rica is described, based on an integrative taxonomic approach that includes the use of light and scanning electron microscopy, ITS2 and 28S rDNA sequencing, and phylogenetic analysis. Anaporrhutum mundae sp. nov. can be distinguished from congeneric species by a combination of morphological traits and particularly by having the genital pore opening at the level of the intestinal bifurcation. The new species also can be distinguished from all other species of Anaporrhutum, except A. euzeti Curran, Blend & Overstreet, 2003, by having fewer testicular follicles per testis. Anaporrhutum mundae sp. nov. also differs from A. euzeti in its forebody shape and by having different morphology and location of the vitellaria. The study of the tegumental surface of A. mundae sp. nov., as revealed by scanning electron microscopy, allowed detection of new morphological characters for a member of Anaporrhutinae that may be of taxonomic value. These are: a stylet cavity dorsal to the oral sucker with a large penetration gland opening on each side of the cavity and small penetration gland openings located ventral to the stylet cavity, arranged in a circle around the mouth. This represents the first record of an Anaporrhutum species from Costa Rica. Further, A. mundae sp. nov. represents the first parasite described or reported in this host.

Design and implementation of an intensive panel survey with refugees and other migrants in need of protection in Costa Rica.

Over the last decade, the global population of refugees and other migrants in need of international protection (MNP) has more than doubled. Despite their rapid growth, panel data collection among MNP remains rare, leaving scholars with few data sources to draw on to understand dynamic changes in their social, economic, legal, or health circumstances. With that paucity in mind, we developed and piloted the Encuesta de Refugiados: Experiencias Sociales y Salud (ERESS), a weekly panel survey conducted with MNP living in Costa Rica. To our knowledge, this panel constitutes one of the first weekly surveys with MNP anywhere in the world. Here, we describe the overall study design, sample recruitment and retention, and key descriptive findings. We show that retaining demographically and socioeconomically diverse MNP in intensive panel surveys is possible and that doing so reveals valuable insights into dynamic changes in their incorporation, family dynamics, and health and wellbeing. By offering a summary of our field experiences and central methodological findings, we highlight the potential benefits and challenges of collecting intensive panel data with MNP, as scholars increasingly seek to understand their pre- and post-migration trajectories and relationships between the two.

Two new species of Epirhyssa (Hymenoptera: Ichneumonidae: Rhyssinae) from Costa Rica.

As a result of continuing research on the ichneumonid wasps of Costa Rica, two new species of Epirhyssa (Rhyssinae) are described: E. leonoreae and E. lewisi. A key is provided for the identification of all 14 species now known to occur in the country.

Review of the Costa Rican Saltagenes Diller, 1995 (Hymenoptera: Ichneumonidae: Ichneumoninae: Phaeogenini) with descriptions of seven new species.

The parasitoid wasp genus Saltagenes Diller, 1995 is known only from the original description of a single species from Argentina. However, undescribed Saltagenes species occur throughout the Neotropical region and into the southern Nearctic. Here, I review the Saltagenes species of Costa Rica and describe seven new species: Saltagenes alboannulatus sp. nov., S. atrosomus sp. nov., S. escazuensis sp. nov., S. gauldi sp. nov., S. modicum sp. nov., S. pseudatrosomus sp. nov., and S. rotundiceps sp. nov. The generic diagnosis is revised to account for hitherto unknown morphological diversity of Saltagenes. An illustrated key and specimen images are provided to aid in identification. Saltagenes is now represented by eight described species though more than double that figure remain undescribed from outside of Costa Rica. More broadly, this study highlights the paucity of our knowledge of Costa Rican Ichneumoninae.

Application of a seismic network to baleen whale call detection and localization in the Panama basin-a Bryde's whale example.

Baleen whales use sounds of various characteristics for different tasks and interactions. This study focuses on recordings from the Costa Rica Rift, in the Eastern Tropical Pacific Ocean, made by 25 ocean-bottom seismographs and a vertical array of 12 hydrophones between January and February 2015. The whale calls observed are of two kinds: more commonly, repetitive 4-5 s-long signals separated into two frequency bands centered at ∼20 and ∼36 Hz; less commonly, a series of ∼0.5 to 1.0 s-long, lower amplitude signals with frequencies between 80 and 160 Hz. These characteristics are similar to calls attributed to Bryde's whales which are occasionally sighted in this region. In this study, the repetitive calls are detected using both the short-term average/long-term average approach and a network empirical subspace detector. In total, 188 and 1891 calls are obtained for each method, demonstrating the value of the subspace detector for highly similar signals. These signals are first localized using a non-linear grid search algorithm and then further relocalized using the double-difference technique. The high-resolution localizations reveal the presence of at least seven whales during the recording period, often crossing the instrument network from southwest to northeast.

Molecular characterization of antibiotic resistant Salmonella enterica across the poultry production chain in Costa Rica: A cross-sectional study.

Antibiotic resistant Salmonella enterica are on the increase, worldwide. Given the scarcity of data, this study aimed to investigate its occurrence, virulence, and antibiotic resistance in Costa Rica's food chain. In total, 65 chicken meat- and 171 chicken caecal samples were collected and examined for Salmonella. High frequencies of Salmonella were found in chicken meat (58.5 %, n/N = 38/65) and poultry farms (38.0 %, n/N = 65/171). The majority of Salmonella from chicken meat (89.5 %, n/N = 34/38) and caecum samples (93.6 %, n/N = 59/63) exhibited multidrug resistance (MDR). Serovar Infantis was the most prevalent (94 %, n/N = 67/71), followed by serovars Anatum and Kentucky (3 %, n/N = 2/71). A pESI-like plasmid (92 %, n/N = 65/71) containing virulence and resistance markers was found in S. Infantis. Given the high prevalence of MDR Salmonella, this study emphasizes the need to enhance surveillance systems for foodborne pathogens and antimicrobial resistance in Costa Rica's food production chain.

A 6-year retrospective study of clinical features, microbiology, and genomics of Shiga toxin-producing Escherichia coli in children who presented to a tertiary referral hospital in Costa Rica.

Shiga-toxin-producing Escherichia coli (STEC) is associated with diarrhea and hemolytic uremic syndrome (HUS). STEC infections in Costa Rica are rarely reported in children. We gathered all the records of STEC infections in children documented at the National Children's Hospital, a tertiary referral hospital, from 2015 to 2020. Clinical, microbiological, and genomic information were analyzed and summarized. A total of 3,768 diarrheal episodes were reviewed. Among them, 31 STEC were characterized (29 fecal, 1 urine, and 1 bloodstream infection). The prevalence of diarrheal disease due to STEC was estimated at 0.8% (n = 29/3,768), and HUS development was 6.4% (n = 2/31). The stx1 gene was found in 77% (n = 24/31) of STEC strains. In silico genomic predictions revealed a predominant prevalence of serotype O118/O152:H2, accompanied by a cluster exhibiting allele differences ranging from 33 to 8, using a core-genome multilocus sequence typing (cgMLST) approach. This is the first study using a genomic approach for STEC infections in Costa Rica.IMPORTANCEThis study provides a comprehensive description of clinical, microbiological, genomic, and demographic data from patients who attended the only pediatric hospital in Costa Rica with Shiga-toxin-producing Escherichia coli (STEC) infections. Despite the low prevalence of STEC infections, we found a predominant serotype O118/O152:H2, highlighting the pivotal role of genomics in understanding the epidemiology of public health threats such as STEC. Employing a genomic approach for this pathogen for the first time in Costa Rica, we identified a higher prevalence of STEC in children under 2 years old, especially those with gastrointestinal comorbidities, residing in densely populated regions. Limitations such as potential geographic bias and lack of strains due to direct molecular diagnostics are acknowledged, emphasizing the need for continued surveillance to uncover the true extent of circulating serotypes and potential outbreaks in Costa Rica.

MEDICAL-SURGICAL MANAGEMENT OF INTESTINAL INFECTION BY PROSTHENORCHIS ELEGANS IN NONHUMAN PRIMATES FROM COSTA RICA.

Parasitism is one of the most important diseases in nonhuman primates (NHP). Parasitism by Prosthenorchis elegans can be a threat to health and conservation of NHP in Costa Rica. Surgical management of intestinal acanthocephalan infection in two squirrel monkeys (Saimiri oerstedii) and one white-faced monkey (Cebus imitator) is described as an alternative to the lack of pharmacologic control options when there is a high burden of parasites present. A complete physical evaluation, including medical ultrasound techniques, allow for diagnosis of the parasite and its lesions. When animals present with a high burden of parasites, surgical management has shown to promote good health outcomes and increase the probability of survival.

Off-premises demand elasticities for pure alcohol in five Latin American countries: The case of Argentina, Chile, Costa Rica, Honduras, and Uruguay.

BACKGROUND AND AIMS: There is ample evidence from high-income countries that fiscal policies such as alcohol taxes can affect the consumption of alcohol by increasing alcohol prices. In the case of Latin American countries, much less is known about how sensitive alcohol demand is to alcohol price changes. This study aims to expand the evidence base on the sensitivity of off-premises pure alcohol demand to price and expenditure increases in five Latin American countries: Argentina, Chile, Costa Rica, Honduras, and Uruguay, which have different socioeconomic profiles and alcohol consumption patterns. DESIGN AND SETTING: Cross-sectional study MEASUREMENTS: The price and expenditure elasticities were estimated using an Almost Ideal Demand System (AIDS). Own price and expenditure elasticities for off-premises pure alcohol were estimated using representative household surveys, which collect data on households' expenses to construct the consumer basket of goods and services used to calculate the consumer price index (CPI) for the country. FINDINGS: Own price elasticities of off-premises pure alcohol for all countries were negative, inelastic, and significant at 1 %. They were -0.418 for Argentina; -0.656 for Chile; and for Costa Rica, Honduras, and Uruguay, they were equal to -0.608, -0.509, and -0.32, respectively. Expenditure elasticities were positive and significant at 1 %, except for Costa Rica, which was significant at 10 %. They were equal to 0.865 in Argentina; 0.943 in Chile; 1.182 in Costa Rica; 0.874 in Honduras; and 0.857 in Uruguay. Elasticities for Costa Rica should be interpreted cautiously, as there is insufficient geographical price variability to identify the demand correctly. CONCLUSIONS: Results were consistent with previous literature for countries from other regions. Governments should expand this study to measure total demand elasticities to improve the design of alcohol tax policies.

Exploration of photoprotective and antibiotic activity of wild Polypodiaceae ferns from Costa Rica.

Skin disorders affect millions of people all over the world. There are limited options to treat dermal illnesses such as vitiligo, psoriasis, and atopic dermatitis (eczema). Central American ferns are a potential source of bioactive metabolites against those diseases. Currently, Polypodium leucotomos Poir. is the only one being commercially utilized for this purpose. In this work, we evaluated the concentration of the skin bioactive compounds: quinic and chlorogenic acid, in the extract of 20 wild ferns from Costa Rica. We also evaluated the antimicrobial capabilities of the crude extracts of wild ferns and the sun protection factor (SPF) of the extracts. We found 19 out of 20 have either an important concentration of the compounds mentioned above or antimicrobial properties. Also, most samples result in higher SPF than P. aureum's rhizome. We also have studied the fern acclimatization, at different shading conditions, finding a significant influence of the culturing conditions on metabolite production. After acclimatization. So far, we demonstrate that various ferns included in this study are a potential source of treatments for skin conditions.

Elevational and seasonal patterns of plant pollinator networks in two highland tropical ecosystems in Costa Rica.

Many plant species in high montane ecosystems rely on animal pollination for sexual reproduction, however, our understanding of plant-pollinator interactions in tropical montane habitats is still limited. We compared species diversity and composition of blooming plants and floral visitors, and the structure of plant-floral visitor networks between the Montane Forest and Paramo ecosystems in Costa Rica. We also studied the influence of seasonality on species composition and interaction structure. Given the severe climatic conditions experienced by organisms in habitats above treeline, we expected lower plant and insect richness, as well as less specialized and smaller pollination networks in the Paramo than in Montane Forest where climatic conditions are milder and understory plants are better protected. Accordingly, we found that blooming plants and floral visitor species richness was higher in the Montane Forest than in the Paramo, and in both ecosystems species richness of blooming plants and floral visitors was higher in the rainy season than in the dry season. Interaction networks in the Paramo were smaller and more nested, with lower levels of specialization and modularity than those in the Montane Forest, but there were no seasonal differences within either ecosystem. Beta diversity analyses indicate that differences between ecosystems are likely explained by species turnover, whereas within the Montane Forest differences between seasons are more likely explained by the rewiring of interactions. Results indicate that the decrease in species diversity with elevation affects network structure, increasing nestedness and reducing specialization and modularity.

The effect of primary healthcare on mortality: Evidence from Costa Rica.

This paper uses the gradual implementation of a primary healthcare (PHC) intervention in Costa Rica to examine the long-term effect of PHC on mortality. Nine years after opening a primary care center, known as a Health Area, there was an associated 13% reduction in age-adjusted mortality rate in the assigned patient population. The effect was highest among adults over 65 years of age and for those with noncommunicable diseases, such as cardiovascular-related causes of death. We also show that as Health Areas opened, more individuals sought care at primary care clinics, while fewer sought care at emergency rooms; these changes may have partially mediated the effect of the intervention on mortality.

A case study on pharmaceutical residues and antimicrobial resistance genes in Costa Rican rivers: A possible route of contamination for feline and other species.

In this investigation, the presence of antibiotics and pharmaceuticals in Costa Rican surface waters, specifically in regions near feline habitats, was examined. The study revealed that 47% of the water samples contained detectable traces of at least one antibiotic. Ciprofloxacin and norfloxacin were the most frequently detected compounds, each with a detection rate of 27%. Other antibiotics, such as erythromycin, roxithromycin, and trimethoprim, were also found but at lower frequencies, around 14%. Notably, all antibiotic concentrations remained below 10 ng/L, with ciprofloxacin, norfloxacin, and erythromycin showing the highest concentrations. Furthermore, the investigation revealed the presence of non-antibiotic pharmaceutical residues in the water samples, typically at concentrations below 64 ng/L. Tramadol was the most frequently detected compound, present in 18% of the samples. The highest concentrations were observed for acetaminophen and tramadol, measuring 64 and 10 ng/L, respectively. Comparing these findings with studies conducted in treated wastewater and urban rivers, it became evident that the concentrations of antibiotics and pharmaceuticals were notably lower in this study. While previous research reported higher values, the limited number of studies conducted in protected areas raises concerns about the potential environmental impact on biodiversity. In summary, these results emphasize the importance of monitoring pharmaceutical residues and antimicrobial resistance genes ARGs in vulnerable ecosystems, especially those in close proximity to feline habitats in Costa Rica. Additionally, the study delved into the detection of (ARGs). All tested water samples were positive for at least one ARG, with the blaTEM gene being the most prevalent at 82%, followed by tetS at 64% and qnrB at 23%. Moreover, this research shed light on the complexity of evaluating ARGs in environmental samples, as their presence does not necessarily indicate their expression. It also highlighted the potential for co-selection and co-regulation of ARGs, showcasing the intricate behaviors of these genes in aquatic environments.

Health inequalities in the geographic distribution of dental practitioners in Costa Rica: An ecological study.

OBJECTIVE: The uneven distribution of dental health services in a territory can cause an imbalance in accessibility, increasing health inequalities. This study aimed to describe the geographical distribution of dental health practitioners according to urbanicity and area-level socio-economic status in Costa Rica. METHODS: A National Dentist Survey was developed to identify employment status, number of working hours, address and list of the working clinics. Data was completed using information from the national College of Surgeons, including all Costa Rican dentists. The Minimal Geographic Units (MGU) allowed for aggregating the population's individual level socio-economic position. Local Potential Accessibility (LPA) calculated the density of full-time hour's equivalents around each MGU using floating sectors. Clinics were geocoded using Geographic Information Systems, creating 2853 clinical points. Distance between each MGU and the nearest accessible clinics considering full-time working hours equivalents was estimated. MGU were divided into six categories: 'No accessibility', 'Very low accessibility', 'Low accessibility', 'Good accessibility' 'High accessibility' and 'Very high accessibility'. RESULTS: Mean national LPA was 6.5 full-time equivalents per 10 000 inhabitants, 3.4% of the Costa Rican population had no access to dentist; 12.9% had very low accessibility, 22.7% had low accessibility, 35.0% had good accessibility, 16.2% had high accessibility, and 9.8% had very high accessibility. Overall, 39% of the population has a rather low accessibility. LPA was higher in urban districts compared to rural districts and in wealthiest districts compared to most disadvantaged districts. Within districts, after adjustment for district's characteristics, LPA was higher in urban MGU compared to rural MGU and in wealthiest MGU compared to most disadvantaged MGU. CONCLUSIONS: This study found that despite having a high number of dentists, their numbers are small in many areas, increasing inequalities in access to health care. The dentist's free establishment, where they can decide to provide private services within a community, creates zones with very high densities, in particular in the wealthiest urban areas, and others with very low densities, in particular the poorest rural areas. The lack of territorial planning has been one of the reasons that has encouraged an imbalance in the availability of dental human resources. To achieve effective universal health coverage, public institutions should focus their efforts on improving access to dental services in underserved areas.

Multivariate study of lice (Insecta: Psocodea: Phthiraptera) assemblages hosted by hummingbirds (Aves: Trochilidae).

Lice were collected from 579 hummingbirds, representing 49 species, in 19 locations in Brazil, Costa Rica, Honduras, Paraguay and Peru, at elevations 0­3000 m above sea level. The following variables were included in an ecological analysis (1) host species' mean body mass, sexual size dimorphism, sexual dichromatism, migratory behaviour and dominance behaviour; (2) mean elevation, mean and predictability of temperature, mean and predictability of precipitation of the host species' geographic area; (3) prevalence and mean abundance of species of lice as measures of infestation. Ordination methods were applied to evaluate data structure. Since the traits are expressed at different scales (nominal, interval and ratio), a principal component analysis based on d-correlations for the traits and a principal coordinates analysis based on the Gower index for species were applied. Lice or louse eggs were found on 80 (13.8%) birds of 22 species. A total of 267 lice of 4 genera, Trochiloecetes, Trochiliphagus, Myrsidea and Leremenopon, were collected, with a total mean intensity of 4.6. There were positive interactions between migration behaviour and infestation indices, with elevational migrants having a higher prevalence and abundance of lice than resident birds. Further, we found weak negative correlations between host body mass and infestation indices and positive correlations between mean elevation and prevalence and abundance of Trochiliphagus. Thus, formerly unknown differences in the ecological characteristics and infestation measures of Trochiliphagus and Trochiloecetes lice were revealed, which allows a better understanding of these associations and their potential impacts on hummingbirds.

Structure and genetic variability of the Costa Rican Paso horse.

The Costa Rican Paso Horse (CPC) is a breed developed in Costa Rica. The objectives were to estimate the genetic structure and evaluate the levels of genetic variability of the population. The genotypes of 14 microsatellites in 3654 records (2052 females and 1602 males) were analyzed. Expected (He) and observed (Ho) heterozygosity, polymorphic information content (CIP), fixation index (FIS), Shannon index, as well as Hardy-Weinberg disequilibrium (DHW) were evaluated. Kinship relationships (Rij) were estimated throughout the entire population. The effective population size (Ne) was calculated, alternating allele frequencies less than 0.05, 0.02 and 0.01. The Bayesian clustering study was carried out to infer how many lines are appropriate from the analysis of genotypes using multiple loci. The number of alleles per locus ranged from 7 to 17, with an average value of 9.6; nine loci presented DHW (P < 0.05); two loci presented negative FIS values, the same as Ho > He; the average of CIP, Ho and He was 0.254, 0.756 and 0.785, respectively. At the 12 loci where He > Ho, the differences ranged from 0.002 to 0.341 (0.036 on average). For Ne, the estimates were 201.9, 230.1, and 241.5. In the Rij, 54.86% of the estimates were in the interval of 0.01 to 77.7%. The number of lines that define the population corresponds to three, with an approximate composition of 33.1%, 32.4% and 34.5%, respectively. The CPC, as a subdivided population with DHW and a reduction in heterozygotes may be associated with possible Wahlund effects. Keywords: Wahlund effect, equines, genetic markers, synthetic breed, Hardy Weinberg.

Comamonas testosteroni as the cause of mortality in embryonated chicken eggs of breeding broiler hens in Costa Rica.

Mortality of chicken embryos and first-week chickens was reported in a commercial incubator company in Costa Rica. Six 1-day-old Cobb chickens and twenty-four embryonated chicken eggs were examined in the Laboratory of Avian Pathology and the Laboratory of Bacteriology of the National University of Costa Rica. Twelve dead-in-shell embryos showed maceration and were immersed in a putrid, turbid, slightly thick brown liquid. Additionally, the other 12 embryonated eggs had milky yellow-orange content. The livers of those embryos had congestion, haemorrhages and multifocal cream foci of necrosis. Granulocytic infiltration was observed in the bursa of Fabricius, myocardium, liver, lung and kidney. Livers and egg yolks from six embryonated chickens and all 1-day-old chickens were aseptically collected and cultured. In addition, tissues from six better conserved embryos and all 1-day-old chickens were fixed in buffered formalin and embedded in paraffin. Biochemical and molecular tests identified Comamonas testosteroni as the cause of the early, middle and late embryo mortality. As all the eggshells from the sampled embryonated eggs were dirty with soiled a fecal matter, contamination after manipulating the eggs was considered the source of infection. C. testosteroni is an environmental microorganism that has rarely been reported to cause human disease. To our knowledge, this is the first report of C. testosteroni causing mortality in a hatchery. Cleaning and disinfection using ozone were implemented in the hatchery to eliminate the embryo mortality associated with C. testosteroni.

Genomic Diversity and Zoonotic Potential of Brucella neotomae.

After reports in 2017 of Brucella neotomae infections among humans in Costa Rica, we sequenced 12 strains isolated from rodents during 1955-1964 from Utah, USA. We observed an exact strain match between the human isolates and 1 Utah isolate. Independent confirmation is required to clarify B. neotomae zoonotic potential.

Cohort profile: evaluation of immune response and household transmission of SARS-CoV-2 in Costa Rica: the RESPIRA study.

PURPOSE: The RESPIRA cohort aims to describe the nature, magnitude, time course and efficacy of the immune response to SARS-CoV-2 infection and vaccination, population prevalence, and household transmission of COVID-19. PARTICIPANTS: From November 2020, we selected age-stratified random samples of COVID-19 cases from Costa Rica confirmed by PCR. For each case, two population-based controls, matched on age, sex and census tract were recruited, supplemented with hospitalised cases and household contacts. Participants were interviewed and blood and saliva collected for antibodies and PCR tests. Participants will be followed for 2 years to assess antibody response and infection incidence. FINDINGS TO DATE: Recruitment included 3860 individuals: 1150 COVID-19 cases, 1999 population controls and 719 household contacts from 304 index cases. The age and regional distribution of cases was as planned, including four age strata, 30% rural and 70% urban. The control cohort had similar sex, age and regional distribution as the cases according to the study design. Among the 1999 controls recruited, 6.8% reported at enrolment having had COVID-19 and an additional 12.5% had antibodies against SARS-CoV-2. Compliance with visits and specimens has been close to 70% during the first 18 months of follow-up. During the study, national vaccination was implemented and nearly 90% of our cohort participants were vaccinated during follow-up. FUTURE PLANS: RESPIRA will enable multiple analyses, including population prevalence of infection, clinical, behavioural, immunological and genetic risk factors for SARS-CoV-2 acquisition and severity, and determinants of household transmission. We are conducting retrospective and prospective assessment of antibody levels, their determinants and their protective efficacy after infection and vaccination, the impact of long-COVID and a series of ancillary studies. Follow-up continues with bimonthly saliva collection for PCR testing and biannual blood collection for immune response analyses. Follow-up will be completed in early 2024. TRIAL REGISTRATION NUMBER: NCT04537338.