RESUMO

Introduction: Mayaro Fever (MF) is a tropical disease caused by the Mayaro virus (MAYV), with outbreaks documented in Latin America. Methods: A hospital-based fever surveillance in Leticia, Colombian Amazon, collected sera from 1,460 patients aged 5-89 between December 2020 and April 2023. Results: Dengue and malaria were the main diagnoses (19.4 and 5.8%, respectively), leaving 71.4% of cases unidentified after testing. Metagenomic sequencing and real-time RT-qPCR testing identified MAYV in two patients (25-year-old male and an 80-year-old female) exhibiting typical symptoms, of MF including rash, joint pain, and fever. Phylogenetics analysis of these two viruses revealed a close relationship to Peruvian strains within the MAYV D genotype. Discussion: The study of AFI in Leticia, Colombia, identified dengue as prevalent, with malaria, COVID-19, Influenza, and Zika viruses also detected. Despite extensive testing, most cases remained unexplained until metagenomic sequencing revealed MAYV, previously unseen in Colombia but known in neighboring countries. Conclusion: This study presents the first near full-length genomes of MAYV in Colombia, highlighting the need for further seroprevalence studies and enhanced surveillance to understand and control the spread of the virus in the region.

RESUMO

Influenza A viruses (IAV) impose significant respiratory disease burdens in both swine and humans worldwide, with frequent human-to-swine transmission driving viral evolution in pigs and highlighting the risk at the animal-human interface. Therefore, a comprehensive One Health approach (interconnection among human, animal, and environmental health) is needed for IAV prevention, control, and response. Animal influenza genomic surveillance remains limited in many Latin American countries, including Colombia. To address this gap, we genetically characterized 170 swine specimens from Colombia (2011-2017). Whole genome sequencing revealed a predominance of pandemic-like H1N1 lineage, with a minority belonging to H3N2 and H1N2 human seasonal-like lineage and H1N1 early classical swine lineages. Significantly, we have identified reassortant and recombinant viruses (H3N2, H1N1) not previously reported in Colombia. This suggests a broad genotypic viral diversity, likely resulting from reassortment between classical endemic viruses and new introductions established in Colombia's swine population (e.g. the 2009 H1N1 pandemic). Our study highlights the importance of a One Health approach in disease control, particularly in an ecosystem where humans are a main source of IAV to swine populations, and emphasizes the need for continued surveillance and enhanced biosecurity measures. The co-circulation of multiple subtypes in regions with high swine density facilitates viral exchange, underscoring the importance of monitoring viral evolution to inform vaccine selection and public health policies locally and globally.

Assuntos

Evolução Molecular , Variação Genética , Vírus da Influenza A Subtipo H1N1 , Vírus da Influenza A Subtipo H3N2 , Infecções por Orthomyxoviridae , Filogenia , Doenças dos Suínos , Animais , Suínos , Colômbia/epidemiologia , Infecções por Orthomyxoviridae/virologia , Infecções por Orthomyxoviridae/veterinária , Infecções por Orthomyxoviridae/epidemiologia , Doenças dos Suínos/virologia , Doenças dos Suínos/epidemiologia , Vírus da Influenza A Subtipo H3N2/genética , Vírus da Influenza A Subtipo H3N2/classificação , Vírus da Influenza A Subtipo H3N2/isolamento & purificação , Vírus da Influenza A Subtipo H1N1/genética , Vírus da Influenza A Subtipo H1N1/classificação , Vírus da Influenza A Subtipo H1N1/isolamento & purificação , Saúde Única , Humanos , Vírus da Influenza A/genética , Vírus da Influenza A/classificação , Vírus da Influenza A/isolamento & purificação , Sequenciamento Completo do Genoma , Genoma Viral , Monitoramento Epidemiológico , Vírus Reordenados/genética , Vírus Reordenados/classificação , Vírus Reordenados/isolamento & purificação , Vírus da Influenza A Subtipo H1N2/genética , Vírus da Influenza A Subtipo H1N2/isolamento & purificação , Vírus da Influenza A Subtipo H1N2/classificação , Influenza Humana/virologia , Influenza Humana/epidemiologia

RESUMO

Equine influenza is a viral disease caused by the equine influenza virus (EIV), and according to the WOAH, it is mandatory to report these infections. In Latin America and Colombia, EIV risk factors have not been analyzed. The objective of this research is to perform an epidemiological and molecular analysis of the EIV in horses with respiratory symptoms from 2020 to 2023 in Colombia. Molecular EIV detection was performed using RT-qPCR and nanopore sequencing. A risk analysis was also performed via the GEE method. A total of 188 equines with EIV respiratory symptoms were recruited. The positivity rate was 33.5%. The descriptive analysis showed that only 12.8% of the horses were vaccinated, and measures such as the quarantine and isolation of symptomatic animals accounted for 91.5% and 88.8%, respectively. The variables associated with the EIV were the non-isolation of positive individuals (OR = 8.16, 95% CI (1.52-43.67), p = 0.014) and sharing space with poultry (OR = 2.16, 95% CI (1.09-4.26), p = 0.027). In conclusion, this is the first EIV investigation in symptomatic horses in Colombia, highlighting the presence of the virus in the country and the need to improve preventive and control measures.

Assuntos

Doenças dos Cavalos , Vírus da Influenza A Subtipo H3N8 , Infecções por Orthomyxoviridae , Cavalos , Animais , Colômbia/epidemiologia , Infecções por Orthomyxoviridae/epidemiologia , Infecções por Orthomyxoviridae/veterinária , Infecções por Orthomyxoviridae/virologia , Doenças dos Cavalos/virologia , Doenças dos Cavalos/epidemiologia , Vírus da Influenza A Subtipo H3N8/isolamento & purificação , Vírus da Influenza A Subtipo H3N8/genética , Feminino , Masculino , Filogenia , Sequenciamento por Nanoporos/métodos , Fatores de Risco

RESUMO

Dengue virus (DENV) is the etiological agent of dengue fever (DF), which is among the most prevalent vector-borne diseases in the tropics. In 2022, the Colombian health surveillance system reported more than 69,000 cases of DF. As part of a hospital-based fever surveillance study, acute-phase sera were collected from 4,545 patients with suspected dengue between 2020 and 2023 in three municipalities of Colombia. Combined reverse transcription-polymerase chain reaction and antigen rapid testing confirmed that 376 patients (8.3%) had DF. The virus was isolated in cell culture from 166 of these patients (44.1%), and genome sequencing was performed successfully on 122 (73.5%). Three DENV serotypes (1, 2, and 3) were identified. Phylogenetic analyses of the DENV-2 sequences revealed that 42 of 50 of the isolates (84%) belonged to the DENV-2 cosmopolitan genotype lineage, clustering with sequences from Asia, Peru, and Brazil. We report the detection, isolation, and whole-genome sequencing (11 Kb) of the DENV-2 cosmopolitan genotype and its recent introduction to Colombia.

Assuntos

Vírus da Dengue , Dengue , Humanos , Sorogrupo , Filogenia , Colômbia/epidemiologia , Genótipo

RESUMO

BACKGROUND: Mansonellosis is an undermapped insect-transmitted disease caused by filarial nematodes that are estimated to infect hundreds of millions of people. Despite their prevalence, there are many outstanding questions regarding the general biology and health impacts of the responsible parasites. Historical reports suggest that the Colombian Amazon is endemic for mansonellosis and may serve as an ideal location to pursue these questions. METHODS: We deployed molecular and classical approaches to survey Mansonella prevalence among adults belonging to indigenous communities along the Amazon River and its tributaries near Leticia, Colombia. RESULTS: Loop-mediated isothermal amplification (LAMP) assays on whole-blood samples detected a much higher prevalence of Mansonella ozzardi infection (approximately 40%) compared to blood smear microscopy or LAMP performed using plasma, likely reflecting greater sensitivity and the ability to detect low microfilaremias and occult infections. Mansonella infection rates increased with age and were higher among men. Genomic analysis confirmed the presence of M. ozzardi that clusters closely with strains sequenced in neighboring countries. We successfully cryopreserved M. ozzardi microfilariae, advancing the prospects of rearing infective larvae in controlled settings. CONCLUSION: These data suggest an underestimation of true mansonellosis prevalence, and we expect that these methods will help facilitate the study of mansonellosis in endemic and laboratory settings.

Assuntos

Mansonelose , Parasitos , Masculino , Adulto , Animais , Humanos , Mansonella/genética , Mansonelose/epidemiologia , Mansonelose/parasitologia , Colômbia/epidemiologia , Prevalência

RESUMO

The first 18 months of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Colombia were characterized by three epidemic waves. During the third wave, from March through August 2021, intervariant competition resulted in Mu replacing Alpha and Gamma. We employed Bayesian phylodynamic inference and epidemiological modeling to characterize the variants in the country during this period of competition. Phylogeographic analysis indicated that Mu did not emerge in Colombia but acquired increased fitness there through local transmission and diversification, contributing to its export to North America and Europe. Despite not having the highest transmissibility, Mu's genetic composition and ability to evade preexisting immunity facilitated its domination of the Colombian epidemic landscape. Our results support previous modeling studies demonstrating that both intrinsic factors (transmissibility and genetic diversity) and extrinsic factors (time of introduction and acquired immunity) influence the outcome of intervariant competition. This analysis will help set practical expectations about the inevitable emergences of new variants and their trajectories. IMPORTANCE Before the appearance of the Omicron variant in late 2021, numerous SARS-CoV-2 variants emerged, were established, and declined, often with different outcomes in different geographic areas. In this study, we considered the trajectory of the Mu variant, which only successfully dominated the epidemic landscape of a single country: Colombia. We demonstrate that Mu competed successfully there due to its early and opportune introduction time in late 2020, combined with its ability to evade immunity granted by prior infection or the first generation of vaccines. Mu likely did not effectively spread outside of Colombia because other immune-evading variants, such as Delta, had arrived in those locales and established themselves first. On the other hand, Mu's early spread within Colombia may have prevented the successful establishment of Delta there. Our analysis highlights the geographic heterogeneity of early SARS-CoV-2 variant spread and helps to reframe the expectations for the competition behaviors of future variants.

Assuntos

COVID-19 , Humanos , Teorema de Bayes , COVID-19/epidemiologia , Colômbia/epidemiologia , SARS-CoV-2/genética

RESUMO

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 continues to threaten public health. The virus is causing breakthrough infections in vaccinated individuals. Also, scarce information is available about cutaneous manifestations after severe acute respiratory syndrome coronavirus 2 infection. CASE PRESENTATION AND FINDINGS: A case of a triple-vaccinated (Pfizer) 37-year-old Hispanic American (Colombian) male who developed urticaria after Omicron BA.5.1 severe acute respiratory syndrome coronavirus 2 breakthrough infection is described. Virus isolation and whole genome sequencing along with immune and molecular assays were performed. Dermatological manifestations (skin rash and urticaria) after Omicron BA.5.1 infection were observed. Sequence analysis of the Omicron BA.5.1 isolate also revealed several important mutations. Hemogram analysis revealed leukocytosis and neutrophilia. Serology testing revealed anti-spike immunoglobulin G serum titers but negative detection of immunoglobulin M at 10 days after symptom onset. Anti-nucleocapsid, anti-spike 1 immunoglobulin G, anti-spike trimer, and anti-receptor-binding-domain immunoglobulin G and immunoglobulin E sera were detected at different titers 10 days after symptom onset. Several serum levels of chemokines/cytokines (Interferon-α, interferon-γ, interleukin-12/interleukin-23p40, interleukin-18, interferon gamma-induced protein-10, monocyte chemoattractant protein-1, monokine induced by gamma, macrophage inflammatory protein-1α, chemokine (C-C motif) ligand-5 , tumor necrosis factor-ß1, Tumor necrosis factor-α) were detected, but interleukin-2, interleukin-4, interleukin-6, interleukin-8, and interleukin-17A were below the limit of detection. INTERPRETATION AND CONCLUSIONS: To our knowledge, this is the first study describing skin effects of a severe acute respiratory syndrome coronavirus 2 Omicron BA.5 variant breakthrough infection in a triple-vaccinated patient in Colombia. Several important mutations were found in the spike glycoprotein of the virus isolated; these mutations are associated with immune evasion and changes in antigenic properties of the virus. Physicians overseeing coronavirus disease 2019 cases should be aware of the potential skin effects of the infection. Pathogenesis of severe acute respiratory syndrome coronavirus 2 infection and its association with proinflammatory cytokines and chemokines may enhance the development of urticaria and other skin manifestations in immunized individuals. However, further studies are needed to better understand the complexity of coronavirus disease in such situations.

Assuntos

COVID-19 , Urticária , Masculino , Humanos , Adulto , Urticária/etiologia , Pele , Citocinas , Anticorpos Antivirais

RESUMO

Arbovirus infections are frequent causes of acute febrile illness (AFI) in tropical countries. We conducted health facility-based AFI surveillance at four sites in Colombia (Cucuta, Cali, Villavicencio, Leticia) during 2019-2022. Demographic, clinical and risk factor data were collected from persons with AFI that consented to participate in the study (n = 2,967). Serologic specimens were obtained and tested for multiple pathogens by RT-PCR and rapid test (Antigen/IgM), with 20.7% identified as dengue positive from combined testing. Oropouche virus (OROV) was initially detected in serum by metagenomic next-generation sequencing (mNGS) and virus target capture in a patient from Cúcuta. Three additional infections from Leticia were confirmed by conventional PCR, sequenced, and isolated in tissue culture. Phylogenetic analysis determined there have been at least two independent OROV introductions into Colombia. To assess OROV spread, a RT-qPCR dual-target assay was developed which identified 87/791 (10.9%) viremic cases in AFI specimens from Cali (3/53), Cucuta (3/19), Villavicencio (38/566), and Leticia (43/153). In parallel, an automated anti-nucleocapsid antibody assay detected IgM in 27/503 (5.4%) and IgG in 92/568 (16.2%) patients screened, for which 24/68 (35.3%) of PCR positives had antibodies. Dengue was found primarily in people aged <18 years and linked to several clinical manifestations (weakness, skin rash and petechiae), whereas Oropouche cases were associated with the location, climate phase, and odynophagia symptom. Our results confirm OROV as an emerging pathogen and recommend increased surveillance to determine its burden as a cause of AFI in Colombia.

Assuntos

Infecções por Bunyaviridae , Humanos , Colômbia/epidemiologia , Filogenia , Infecções por Bunyaviridae/complicações , Infecções por Bunyaviridae/epidemiologia

RESUMO

Biosecurity protocols (BP) and good management practices are key to reduce the risk of introduction and transmission of infectious diseases into the pig farms. In this observational cross-sectional study, survey data were collected from 176 pig farms with inventories over 100 sows in Colombia. We analyzed a complex survey dataset to explore the structure and identify clustering patterns using Multiple Correspondence Analysis (MCA) of swine farms in Colombia, and estimated its association with Influenza A virus detection. Two principal dimensions contributed to 27.6% of the dataset variation. Farms with highest contribution to dimension 1 were larger farrow-to-finish farms, using self-replacement of gilts and implementing most of the measures evaluated. In contrast, farms with highest contribution to dimension 2 were medium to large farrow-to-finish farms, but implemented biosecurity in a lower degree. Additionally, two farm clusters were identified by Hierarchical Cluster Analysis (HCA), and the odds of influenza A virus detection was statistically different between clusters (OR 7.29, CI: 1.7,66, p = < 0.01). Moreover, after logistic regression analysis, three important variables were associated with higher odds of influenza detection: (1) "location in an area with a high density of pigs", (2) "farm size", and (3) "after cleaning and disinfecting, the facilities are allowed to dry before use". Our results revealed two clustering patterns of swine farms. This systematic analysis of complex survey data identified relationships between biosecurity, husbandry practices and influenza status. This approach helped to identify gaps on biosecurity and key elements for designing successful strategies to prevent and control swine respiratory diseases in the swine industry.

RESUMO

Background: Influenza A virus (IAV) surveillance in swine is critical not only due to the direct impact of the disease in the pork industry but also because IAV are prone to interspecies transmission (from human to pigs and vice versa); therefore, its monitoring is fundamental from a public and animal health perspective. Several diagnostic techniques have been used to detect IAV infection from nasal samples in swine, while samples of oral fluids (OF) are in use as novel alternatives for pathogen detection. The OF allow for efficient and feasible low-cost disease detection at the herd level, with low risk of stress for the animals. Objective: To describe a surveillance strategy of IAV at the herd level during respiratory disease outbreaks in swine farms at tropical settings using porcine oral fluids. Methods: An active surveillance strategy was conducted in several farms with past records of respiratory disease. The IAV detection was conducted in five purposively selected swine farms from years 2014 to 2017. We investigated a total of 18 respiratory outbreaks of the disease. Swine OF were collected for IAV testing. An OF sample is described as a pen-based specimen collected from a group of >20 pigs per pen and/or per barn (stall-housed individually with close contact among them). The IAV infection was investigated in OF by rRT-PCR testing and confirmed by viral isolation in cell culture Results: We found 107 (7.4%) positives to IAV by rRT-PCR from a total of 1,444 OF samples tested. Additionally, 9 IAV isolates were all further identified as H1 subtype. Conclusions: Our results demonstrate that OF can be easily implemented as a novel, user-friendly, welfare-friendly, accurate and cost-effective sampling method for active surveillance and monitoring of IAV infections in swine farms in tropical settings.

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Antecedentes: La vigilancia del Virus Influenza A (IAV) en los cerdos es fundamental debido al impacto directo de la enfermedad en la industria porcina, pero también porque los IAV son propensos de transmisión entre especies (humanos a cerdos y viceversa), y por lo tanto su monitoreo es crítico desde las perspectivas de salud pública y animal. Actualmente existen varias técnicas de diagnóstico disponibles para detectar la infección por IAV a partir de muestras nasales en cerdos, sin embargo, se han implementado otras muestras como los fluidos orales (OF) como nuevas alternativas para la detección de patógenos. El OF permite una detección eficiente y factible de enfermedades a menor costo a nivel de rebaño, con menor riesgo de estrés para los animales. Objetivo: Describir una estrategia de vigilancia de IAV a nivel de hato por medio de fluidos orales porcinos durante brotes de enfermedades respiratorias en granjas porcinas en entornos tropicales. Métodos: Se llevó a cabo una estrategia de vigilancia activa en cinco granjas porcinas seleccionadas con antecedentes de enfermedades respiratorias. Se recolectaron OF porcinos para la prueba de IAV. Una muestra de OF se describió como una muestra grupal recolectada de un grupo de >20 cerdos por corral y/o por establo (si estaban alojados individualmente, pero tenían un contacto cercano entre ellos). La infección por IAV se investigó probando OF mediante rRT-PCR y la confirmación mediante aislamiento viral en cultivo celular. Resultados: La detección de IAV se llevó a cabo en cinco granjas seleccionadas intencionalmente entre 2014- 2017. Investigamos un total de 18 eventos de brotes de enfermedades respiratorias. Del total de 1.444 OF muestras analizadas, encontramos 107 (7,4%) positivos a IAV mediante rRT-PCR. Además, solo se obtuvieron 9 aislamientos de IAV y todos se identificaron además como subtipo H1. Conclusiones: Los resultados de nuestro estudio demostraron cómo la OF puede implementarse fácilmente como un método de muestreo novedoso, fácil de usar, amigable con el bienestar animal, preciso y rentable para la vigilancia activa y el monitoreo de infecciones por IAV en granjas porcinas en entornos tropicales.

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Antecedentes: A vigilância do vírus Influenza A (IAV) em suínos é crítica devido ao impacto direto da doença na indústria de suínos, mas também porque os IAV são propensos a transmissão interespécies (de humanos para porcos e vice-versa) e, portanto, seu monitoramento é crítico do ponto de vista da saúde pública e animal. Atualmente, existem várias técnicas de diagnóstico disponíveis para detectar a infecção por IAV em amostras nasais de suínos, no entanto, outras amostras, como fluidos orais (OF), têm sido implementadas como novas alternativas para a detecção de patógenos. O OF permite uma detecção eficiente e viável de doenças com menor custo em nível de rebanho, com menor risco de estresse para os animais. Objetivo: Descrever uma estratégia de vigilância de IAV em nível de rebanho durante surtos de doenças respiratórias em granjas de suínos em ambientes tropicais por meio de fluidos orais suínos. Métodos: A estratégia de vigilância ativa foi conduzida em cinco granjas de suínos selecionadas com histórico de doenças respiratórias. Suínos OF foram coletados para teste de IAV. Uma amostra OF foi descrita como um espécime baseado em curral coletado de um grupo de >20 porcos por curral e/ou por celeiro (se eles foram alojados individualmente, mas tendo contato próximo entre eles). A infecção IAV foi investigada testando OF por rRT-PCR e confirmada por isolamento em cultura de células. Resultados: A detecção do IAV foi realizada em cinco fazendas selecionadas propositalmente entre 2014-2017. Nós investigamos um total de 18 eventos de surto de doença respiratória. Do total de 1.444 amostras de OF testadas, encontramos 107 (7,4%) positivas para IAV por rRT-PCR. Além disso, apenas 9 isolados de IAV foram obtidos, e todos foram posteriormente identificados como subtipo H1. Conclusão: Os resultados de nosso estudo demonstraram como o OF pode ser facilmente implementado como um método de amostragem novo, amigável, amigável com o bem-estar, preciso e de baixo custo para vigilância ativa e monitoramento de infecções IAV em fazendas de suínos em ambientes tropicais.

Assuntos

COVID-19 , SARS-CoV-2 , COVID-19/epidemiologia , Colômbia/epidemiologia , Humanos

RESUMO

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to cause very high morbidity and mortality throughout Latin American countries. However, few population-based seroprevalence surveys have been conducted to quantify attack rates and characterize drivers of transmission. METHODS: We conducted a population-based cross-sectional study to assess the seroprevalence of antibodies against SARS-CoV-2 in ten cities in Colombia between September and December 2020. The study involved multi-stage cluster sampling at each city. Participants provided a serum sample and answered a demographic and risk factor questionnaire. Prior infection by SARS-CoV-2 was ascertained using the "SARS-CoV-2 Total (COV2T) Advia Centaur - Siemens" chemiluminescence assay. FINDINGS: A total of 17863 participants from 7320 households participated in the study. Seroprevalence varied substantially between cities, ranging from 26% (95%CI 23-29 %) in Medellín to 68% (95%CI 62-74 %) in Guapi. There were no differences in seroprevalence by sex, but seropositivity was higher in certain ethnic groups. There was substantial heterogeneity in seroprevalence within cities, driven to a large extent by a strong association between socioeconomic stratum and seropositivity. INTERPRETATION: Colombia has been one of the Latin American countries most affected by the COVID-19 pandemic. This study documented very high attack rates in several Colombian cities by the end of 2020 and identified key drivers of heterogeneities including ethnicity and socioeconomic stratum. Few studies of seroprevalence of SARS-CoV-2 have been conducted in Latin America, and therefore this study contributes to the fundamental understanding of the pandemic in the region. FUNDING: The study was sponsored by, Ministerio de Ciencia y Tecnología e Innovación -CT361/2020, Ministerio de Salud y Protección Social, Fundación Universitaria del Norte, Imperial College of London, Universidad Nacional de Colombia (Sede Medellín), Universidad de Córdoba, California University, Unidad Nacional de Gestión del Riesgo, Centro de Atención y Diagnóstico de Enfermedades Infecciosas -CDI-, Centro Internacional de Entrenamiento e Investigaciones Médicas -CIDEIM-, Departamento Administrativo Nacional de Estadística - DANE, Fondo Nacional de Turismo -FONTUR-, Secretarías de Salud Departamentales, Distritales y Municipales and Instituto Nacional de Salud.

RESUMO

Timely and accurate diagnostics are essential to fight the COVID-19 pandemic, but no test satisfies both conditions. Dogs can scent-identify the unique odors of volatile organic compounds generated during infection by interrogating specimens or, ideally, the body of a patient. After training 6 dogs to detect SARS-CoV-2 by scent in human respiratory secretions (in vitro diagnosis), we retrained 5 of them to search and find the infection by scenting the patient directly (in vivo screening). Then, efficacy trials were designed to compare the diagnostic performance of the dogs against that of the rRT-PCR in 848 human subjects: 269 hospitalized patients (COVID-19 prevalence 30.1%), 259 hospital staff (prevalence 2.7%), and 320 government employees (prevalence 1.25%). The limit of detection in vitro was lower than 10-12 copies ssRNA/mL. During in vivo efficacy experiments, our 5 dogs detected 92 COVID-19 positive patients among the 848 study subjects. The alert (lying down) was immediate, with 95.2% accuracy and high sensitivity (95.9%; 95% C.I. 93.6-97.4), specificity (95.1%; 94.4-95.8), positive predictive value (69.7%; 65.9-73.2), and negative predictive value (99.5%; 99.2-99.7) in relation to rRT-PCR. Seventy-five days after finishing in vivo efficacy experiments, a real-life study (in vivo effectiveness) was executed among the riders of the Metro System of Medellin, deploying the human-canine teams without previous training or announcement. Three dogs were used to examine the scent of 550 volunteers who agreed to participate, both in test with canines and in rRT-PCR testing. Negative predictive value remained at 99.0% (95% C.I. 98.3-99.4), but positive predictive value dropped to 28.2% (95% C.I. 21.1-36.7). Canine scent-detection in vivo is a highly accurate screening test for COVID-19, and it detects more than 99% of infected individuals independent of key variables, such as disease prevalence, time post-exposure, or presence of symptoms. Additional training is required to teach the dogs to ignore odoriferous contamination under real-life conditions.

Assuntos

COVID-19/diagnóstico , Odorantes/análise , Feromônios/análise , Animais , Cães , Feminino , Humanos , Masculino , Programas de Rastreamento , Valor Preditivo dos Testes , SARS-CoV-2/patogenicidade , Sensibilidade e Especificidade , Compostos Orgânicos Voláteis , Cães Trabalhadores

RESUMO

The mechanical properties of metallic alloys are controlled through the design of their polycrystalline structure via heat treatments. For single-phase microstructures, they aim to achieve a particular average grain diameter to leverage stress hardening or softening. The stochastic nature of the recrystallization process generates a grain size distribution, and the randomness of the crystallographic orientation determines the anisotropy of a mechanical response. We developed a multiscale computational formalism to capture the collective mechanical response of polycrystalline microstructures at unprecedented length scales. We found that for an averaged grain size, the mechanical response is highly dependent on the grain size distribution. The simulations reveal the topological conditions that promote coherent grain texturization and grain growth inhibition during stress relaxation. We identify the microstructural features that are responsible for the appearance of stress hotspots. Our results provide the elusive evidence of how stress hotspots are ideal precursors for plastic and creep failure.

RESUMO

The assembly of nematic colloids relies on long-range elastic interactions that can be manipulated through external stimuli. Confinement and the presence of a hydrodynamic field alter the defect structures and the energetic interactions between the particles. In this work, the assembly landscape of nanoparticles embedded in a nematic liquid crystal confined in a nanochannel under a pressure-driven flow is determined. The dynamics of the liquid crystal tensor alignment field is determined through a Poisson-Bracket framework, namely the Stark-Lubensky equations, coupled with the zero-Reynolds momentum equations and the liquid crystal Landau-de Gennes free energy functional. A second order semi-implicit time integration and a three-dimensional Galerkin finite element method are used to resolve flow and nematic fields under several conditions. In general, the zero Reynolds flow displaces the defects around the particles in the upstream direction and renders the surface anchoring ineffective when the flow strength dominates over the nematic elasticity. More importantly, the potential of mean force for particle assembly is non-monotonic independent of surface anchoring. Our results show that the confinement length scale determines the repulsion/attraction transition between colloids, while the flow strength modifies the static defect structure surrounding the particles and determines the magnitude of the energetic barrier for successful assembly. In the attractive regime, the particles move at different rates through the nematic until one particle eventually catches up with the other. This process occurs against or along the direction of flow depending on the flow strength. Ultimately, these results provide a template for engineering and controlling the transport and assembly of nanoparticles under far-from equilibrium conditions in anisotropic media.

RESUMO

The design of polymeric membranes for proton or ionic exchange highly depends on the fundamental understanding of the physical and molecular mechanisms that control the formation of the conduction channels. There is an inherent relation between the dynamical structure of the polymeric membrane and the electrostatic forces that drive membrane segregation and proton transport. Here, we used a multi-scale computational approach to analyze the morphology of sulfonated poly(ether ether ketone) membranes at the mesoscale. A self-consistent description of the electrostatic phenomenon was adopted, where discrete polymer chains and a continuum proton field were embedded in a continuum fluid. Brownian dynamics was used for the evolution of the suspended polymer molecules, while a convection-diffusion transport equation, including the Nernst-Planck diffusion mechanism, accounted for the dynamics of the proton concentration field. We varied the polymer concentration, the degree of sulfonation and the level of confinement to find relationships between membrane structure and proton conduction. Our results indicate that the reduced mobility of polymer chains, at concentrations above overlap, and a moderate degree of sulfonation - i.e., 30% - are essential elements for membrane segregation and proton domain connectivity. These conditions also ensure that the membrane structure is not affected by size or by potential gradients. Importantly, our analysis shows that membrane conductivity and current are linearly dependent on polymer concentration and quadratically dependent on the degree of sulfonation. We found that the optimal polymeric membrane design requires a polymer concentration above overlap and a degree of sulfonation around 50%. These conditions promote a dynamical membrane morphology with a constant density of proton channels. Our results and measurements agree with previous experimental works, thereby validating our model and observations.

RESUMO

In this work, we explore fluctuations during phase transitions of uniaxial and biaxial liquid crystals using a phenomenological free energy functional. We rely on a continuum-level description of the liquid crystal ordering with a tensorial parameter and a temperature dependent Landau polynomial expansion of the tensor's invariants. The free energy functional, over a three-dimensional periodic domain, is integrated with a Gaussian quadrature and minimized with a theoretically informed Monte Carlo method. We reconstruct analytical phase diagrams, following Landau and Doi's notations, to verify that the free energy relaxation reaches the global minimum. Importantly, our relaxation method is able to follow the thermodynamic behavior provided by other non-phenomenological approaches; we predict the first order character of the isotropic-nematic transition, and we identify the uniaxial-biaxial transition as second order. Finally, we use a finite-size scaling method, using the nematic susceptibility, to calculate the transition temperatures for 4-Cyano-4'-pentylbiphenyl (5CB) and N-(4-methoxybenzylidene)-4-butylaniline (MBBA). Our results show good agreement with experimental values, thereby validating our minimization method. Our approach is an alternative towards the relaxation of temperature dependent continuum-level free energy functionals, in any geometry, and can incorporate complicated elastic and surface energy densities.

RESUMO

The transition temperatures of nanoscale polymeric films are measured from a leveling experiment where a designed nanostructure is heated from below. Surface tension forces drive the relaxation of the polymeric features, allowing direct measurement of the critical temperature of collapse, Tflow, and indirect measurement of the glass transition temperature, TG. Small-angle X-ray scattering and atomic force microscopy are used to follow the leveling dynamics, whereas a mathematical model for the momentum balance is implemented to extract the viscosity of the polymer film as a function of temperature. Our methodology is illustrated in the context of films of poly(methyl methacrylate) that are patterned via nanoimprint lithography into dense gratings. We study how the glass transition temperature and the critical temperature of collapse vary as a function of the film size and the inclusion of the antiplasticizer, tris(2-chloropropyl) phosphate. The grating periods are varied consistently between 80 and 240 nm, whereas the antiplasticizer concentrations are 1, 3, 5, and 10 wt %. The solution of the momentum balance allows the detailed correlation between stresses, curvature, heating, and shear rates during leveling. We found that both temperatures, TG and Tflow, decrease as the film size decreases or as the concentration of the antiplasticizer increases. In addition, antiplasticizer concentrations between 3 and 5 wt % stabilize the size dependence of Tflow. We show that the nature of the antiplasticizer is effectively to increase the low-temperature viscosity of the film. However, during leveling, the antiplasticized film sustains its curvature, thereby driving a sudden relaxation, once TG is reached, and increasing the possibilities of defects.

RESUMO

Electrostatic forces greatly affect the overall dynamics and diffusional activities of suspended charged particles in crowded environments. Accordingly, the concentration of counter- or co-ions in a fluid-''the salt"-determines the range, strength, and order of electrostatic interactions between particles. This environment fosters engineering routes for controlling directed assembly of particles at both the micro- and nanoscale. Here, we analyzed two computational modeling schemes that considered salt within suspensions of charged particles, or polyelectrolytes: discrete and continuum. Electrostatic interactions were included through a Green's function formalism, where the confined fundamental solution for Poisson's equation is resolved by the general geometry Ewald-like method. For the discrete model, the salt was considered as regularized point-charges with a specific valence and size, while concentration fields were defined for each ionic species for the continuum model. These considerations were evolved using Brownian dynamics of the suspended charged particles and the discrete salt ions, while a convection-diffusion transport equation, including the Nernst-Planck diffusion mechanism, accounted for the dynamics of the concentration fields. The salt/particle models were considered as suspensions under slit-confinement conditions for creating crowded "macro-ions", where density distributions and radial distribution functions were used to compare and differentiate computational models. Importantly, our analysis shows that disparate length scales or increased system size presented by the salt and suspended particles are best dealt with using concentration fields to model the ions. These findings were then validated by novel simulations of a semipermeable polyelectrolyte membrane, at the mesoscale, from which ionic channels emerged and enable ion conduction.