https://www.scielo.br/j/jbn/a/XCDXYHCGzjjG8sWsb8KGB3R/ / Infarto renal bilateral em paciente com infecção grave por COVID-19

Abstract Thromboembolic events are frequent in patients with COVID-19 infection, and no cases of bilateral renal infarctions have been reported. We present the case of a 41-year-old female patient with diabetes mellitus and obesity who attended the emergency department for low back pain, respiratory failure associated with COVID-19 pneumonia, diabetic ketoacidosis, and shock. The patient had acute kidney injury and required hemodialysis. Contrast abdominal tomography showed bilateral renal infarction and anticoagulation was started. Kidney infarction cases require high diagnostic suspicion and possibility of starting anticoagulation.

Resumo Fenômenos tromboembólicos são frequentes em pacientes com infecção por COVID-19 e nenhum caso de infarto renal bilateral havia sido relatado. Apresentamos o caso de uma paciente do sexo feminino, de 41 anos, com diabetes mellitus e obesidade, que deu entrada no serviço de urgência por lombalgia, insuficiência respiratória associada à pneumonia COVID-19, cetoacidose diabética e choque. A paciente apresentava lesão renal aguda e demandava hemodiálise. A tomografia abdominal contrastada mostrou infarto renal bilateral e foi iniciada anticoagulação. Os casos de infarto renal requerem alta suspeita diagnóstica e possibilidade de iniciar a anticoagulação.

Seroprevalence of IgM and IgG Antibodies against SARS-CoV-2 in Asymptomatic People in Wuhan: Data from a General Hospital Near South China Seafood Wholesale Market during March to April in 2020 / 生物医学与环境科学（英文）

The aim of this study was to estimate the seroprevalence of immunoglobulin M (IgM) and G (IgG) antibodies against SARS-CoV-2 in asymptomatic people in Wuhan. This was a cross-sectional study, which enrolled 18,712 asymptomatic participants from 154 work units in Wuhan. Pearson Chi-square test,

Effects of angiotensin II receptor blocker usage on viral load, antibody dynamics, and transcriptional characteristics among COVID-19 patients with hypertension / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Epidemiological evidence suggests that patients with hypertension infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are at increased risk of acute lung injury. However, it is still not clear whether this increased risk is related to the usage of renin-angiotensin system (RAS) blockers. We collected medical records of coronavirus disease 2019 (COVID-19) patients from the First Affiliated Hospital, Zhejiang University School of Medicine (Hangzhou, China), and evaluated the potential impact of an angiotensin II receptor blocker (ARB) on the clinical outcomes of COVID-19 patients with hypertension. A total of 30 hypertensive COVID-19 patients were enrolled, of which 17 were classified as non-ARB group and the remaining 13 as ARB group based on the antihypertensive therapies they received. Compared with the non-ARB group, patients in the ARB group had a lower proportion of severe cases and intensive care unit (ICU) admission as well as shortened length of hospital stay, and manifested favorable results in most of the laboratory testing. Viral loads in the ARB group were lower than those in the non-ARB group throughout the disease course. No significant difference in the time of seroconversion or antibody levels was observed between the two groups. The median levels of soluble angiotensin-converting enzyme 2 (sACE2) in serum and urine samples were similar in both groups, and there were no significant correlations between serum sACE2 and biomarkers of disease severity. Transcriptional analysis showed 125 differentially expressed genes which mainly were enriched in oxygen transport, bicarbonate transport, and blood coagulation. Our results suggest that ARB usage is not associated with aggravation of COVID-19. These findings support the maintenance of ARB treatment in hypertensive patients diagnosed with COVID-19.

Development and validation of an individualized nomogram for early prediction of the duration of SARS-CoV-2 shedding in COVID-19 patients with non-severe disease / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

With the number of cases of coronavirus disease-2019 (COVID-19) increasing rapidly, the World Health Organization (WHO) has recommended that patients with mild or moderate symptoms could be released from quarantine without nucleic acid retesting, and self-isolate in the community. This may pose a potential virus transmission risk. We aimed to develop a nomogram to predict the duration of viral shedding for individual COVID-19 patients. This retrospective multicentric study enrolled 135 patients as a training cohort and 102 patients as a validation cohort. Significant factors associated with the duration of viral shedding were identified by multivariate Cox modeling in the training cohort and combined to develop a nomogram to predict the probability of viral shedding at 9, 13, 17, and 21 d after admission. The nomogram was validated in the validation cohort and evaluated by concordance index (C-index), area under the curve (AUC), and calibration curve. A higher absolute lymphocyte count (

La salud pública en la primera ola: una agenda para la cooperación ante Covid-19 / Public health in the first wave: a research agenda for cooperation under Covid-19

Resumen El Covid-19 representa uno de los retos más grandes en la historia reciente de la salud pública. Es fundamental que se fortalezcan los lazos de cooperación científica bajo un objetivo común: proteger la salud de la población. En este artículo se presentan ideas que necesitan un desarrollo urgente y colaborativo. Se discute la estimación de la magnitud de la epidemia mediante un panel nacional de seroprevalencia y nuevas estrategias para mejorar el monitoreo en tiempo real de la epidemia. También se analizan las externalidades negativas asociadas con la respuesta a la pandemia. Finalmente, se presenta un marco general para el desarrollo de ideas para salir del confinamiento, resaltando la importancia de implementar acciones estructurales, sostenibles y equitativas. Se hace un llamado a la solidaridad y la cooperación, donde nuestros esfuerzos y creatividad se dediquen a la resolución de los problemas que enfrentan México y el mundo.

Abstract Covid-19 represents one of the largest challenges in the recent history of public health. It is fundamental that we strengthen scientific cooperation under a common goal: to protect the health of the population. In this article, we present ideas that need urgent and collaborative efforts. We discuss the estimation of the magnitude of the epidemic through a nationwide seroprevalence panel, as well as new strategies to monitor the epidemic in real time. We also analyze the negative externalities associated to the pandemic. Finally, we present a general framework to develop ideas to come out of the lockdown, highlighting the importance of implementing sustainable and equitable structural interventions. We call for solidarity and cooperation, focusing our efforts and creativity in the resolution of the problems that currently affect Mexico and the world.

Infusion of convalescent plasma is associated with clinical improvement in critically ill patients with Covid-19: a pilot study

ABSTRACT Background: The ideal treatment of coronavirus disease (COVID)-19 has yet to be defined, but convalescent plasma (CoPla) has been successfully employed. Objective: The objective of the study was to study the safety and outcomes of the administration of CoPla to individuals with severe COVID-19 in an academic medical center. Methods: Ten patients were prospectively treated with plasma from COVID-19 convalescent donors. Results: Over 8 days, the sequential organ failure assessment score dropped significantly in all patients, from 3 to 1.5 (p = 0.014); the Kirby index (PaO2/FiO2) score increased from 124 to 255, (p < 0.0001), body temperature decreased significantly from 38.1 to 36.9°C (p = 0.0058), and ferritin levels also dropped significantly from 1736.6 to 1061.8 ng/ml (p = 0.0001). Chest X-rays improved in 7/10 cases and in 6/10, computerized tomography scans also revealed improvement of the lung injury. Decreases in C-reactive protein and D-dimer levels were also observed. Three of five patients on mechanical ventilation support could be extubated, nine were transferred to conventional hospital floors, and six were sent home; two patients died. The administration of CoPla had no side effects and the 24-day overall survival was 77%. Conclusions: Although other treatments were also administered to the patients and as a result data are difficult to interpret, it seems that the addition of CoPla improved pulmonary function.

COVID-19: a meta-analysis of diagnostic test accuracy of commercial assays registered in Brazil

ABSTRACT The accuracy of commercially available tests for COVID-19 in Brazil remains unclear. We aimed to perform a meta-analysis to describe the accuracy of available tests to detect COVID-19 in Brazil. We searched at the Brazilian Health Regulatory Agency (ANVISA) online platform to describe the pooled sensitivity (Se), specificity (Sp), diagnostic odds ratio (DOR) and summary receiver operating characteristic curves (SROC) for detection of IgM/IgG antibodies and for tests using naso/oropharyngeal swabs in the random-effects models. We identified 16 tests registered, mostly rapid-tests. Pooled diagnostic accuracy measures [95%CI] were: (i) for IgM antibodies Se = 82% [76-87]; Sp = 97% [96-98]; DOR = 168 [92-305] and SROC = 0.98 [0.96-0.99]; (ii) for IgG antibodies Se = 97% [90-99]; Sp = 98% [97-99]; DOR = 1994 [385-10334] and SROC = 0.99 [0.98-1.00]; and (iii) for detection of SARS-CoV-2 by antigen or molecular assays in naso/oropharyngeal swabs Se = 97% [85-99]; Sp = 99% [77-100]; DOR = 2649 [30-233056] and SROC = 0.99 [0.98-1.00]. These tests can be helpful for emergency testing during the COVID-19 pandemic in Brazil. However, it is important to highlight the high rate of false negative results from tests which detect SARS-CoV-2 IgM antibodies in the initial course of the disease and the scarce evidence-based validation results published in Brazil. Future studies addressing the diagnostic performance of tests for COVID-19 in the Brazilian population are urgently needed.

Serum levels of matrix metalloproteinase-2, -9, and vitamin D in patients with multiple sclerosis with or without herpesvirus-6 seropositivity

ABSTRACT In recent years, extreme attention has been focused on the role of human herpesvirus-6 (HHV-6) in multiple sclerosis (MS) pathogenesis. However, the pathogenesis of MS associated with HHV-6 infection remains unknown. In this study, we measured the serum levels of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), and vitamin D levels in MS patients with HHV-6 infection and MS patients without HHV-6 infection. Five hundred sixty (including 300 females and 260 males) MS patients along with 560 healthy subjects were analyzed for HHV-6 seropositivity using enzyme-linked immunosorbent assay (ELISA). Subsequently, we measured the serum levels of MMP-2, MMP-9, and vitamin D levels in MS patients with HHV-6 infection and MS patients without HHV-6 infection by ELISA. About 90.7% of MS patients (508/560) were seropositive for HHV-6, while 82.3% (461/560) of healthy subjects were seropositive for this virus (p = 0.001). Moreover, there was a significant increase in the levels of MMP-2, MMP-9, and lower vitamin D in the serum samples of MS patients when compared with healthy subjects. Additionally, we demonstrated that the MMP-9 levels in seropositive MS patients were significantly higher than seronegative MS patients (p = 0.001). Finally, our results demonstrated that the mean of expanded disability status scale (EDSS) in seropositive MS patients was significantly higher in comparison to seronegative MS patients (p < 0.05). In conclusion, we suggest that the HHV-6 infection may play a role in MS pathogenesis.

Seroprevalence of chikungunya virus infection in five hospitals within Anyigba, Kogi State of Nigeria

ABSTRACT Febrile illnesses in developing countries are often misdiagnosed as malaria or typhoid fever. Although arboviral infections have similar clinical symptoms, they are usually not screened because of limited resources and the fact that there are several viruses in this group. Chikungunya virus (CHIKV) has been isolated in parts of Nigeria, but there is no documented evidence of the infection in Kogi State. This study determined seroprevalence of active and past CHIKV infection among febrile patients who tested negative for malaria and typhoid fever. Sera from 243 febrile patients were screened for CHIKV IgG and IgM using an immunochromatographic test kit. Clinical and socio-demographic variables were collected using a structured questionnaire. Recent CHIKV infection was observed in 5.8% of the study participants while 25.1% had IgG antibodies demonstrating previous infection. Significant associations were observed between seropositivity and age of participants (p < 0.001), sex (p = 0.044), marital status (p = 0.002), and occupation (p < 0.001). Clinical symptoms such as fever, joint pain, and headache were significantly associated with seropositivity. This study identified recent CHIKV infection in Anyigba. Therefore, there is need for routine screening of febrile patients and molecular characterization to determine the nature of circulating strains.

Are SARS-CoV-2 reinfection and Covid-19 recurrence possible? a case report from Brazil

Abstract With the large number of individuals infected and recovered from Covid-19, there is intense discussion about the quality and duration of the immunity elicited by SARS-CoV-2 infection, including the possibility of disease recurrence. Here we report a case with strong clinical, epidemiological and laboratorial evidence of, not only reinfection by SARS-CoV-2, but also clinical recurrence of Covid-19.

EPICOVID19 protocol: repeated serological surveys on SARS-CoV-2 antibodies in Brazil / Protocolo EPICOVID19: pesquisas sorológicas repetidas de anticorpos SARS-CoV-2 no Brasil

Abstract The first case of COVID-19 was reported in China in December 2019, and, as the virus has spread worldwide, the World Health Organization declared it a pandemic. Estimates on the number of COVID-19 cases do not reflect it real magnitude as testing is limited. Population based data on the proportion of the population with antibodies is relevant for planning public health policies. We aim to assess the prevalence of SARS-CoV-2 antibodies, presence of signs and symptoms of COVID-19, and adherence to isolation measures. A random sample comprising 133 sentinel cities from all states of the country will be selected. Three serological surveys, three weeks apart, will be conducted. The most populous municipality in each intermediate region of the country, defined by the Brazilian Institute of Geography and Statistics, was chosen as sentinel city. In each city, 25 census tracts will be selected, and 10 households will be systematically sampled in each tract, totaling 33,250 participants. In each household, one inhabitant will be randomly selected to be interviewed and tested for antibodies against SARS-CoV-2, using WONDFO SARS-CoV-2 Antibody Test. By evaluating a representative sample of Brazilian sentinel sites, this study will provide essential information for the design of health policies.

Resumo O COVID-19 é causado pelo vírus SARS-CoV-2, sendo o primeiro caso relatado na China em dezembro de 2019. O vírus se espalhou pelo mundo, levando a Organização Mundial da Saúde a declarar uma pandemia. As estimativas do número de casos de COVID-19 não refletem sua magnitude real, pois os testes são limitados em muitos países. Dados populacionais sobre a proporção da população com anticorpos são relevantes para o planejamento de políticas públicas de saúde. Nosso objetivo é avaliar a prevalência de anticorpos SARS-CoV-2, a presença de sinais e de sintomas de COVID-19 e a adesão a medidas de isolamento. Uma amostra aleatória composta por 133 cidades sentinelas de todos os estados do país será selecionada. Serão realizados três levantamentos sorológicos, com três semanas de intervalo. Em cada cidade, serão selecionados 25 setores censitários e 10 famílias serão amostradas aleatoriamente em cada setor. Em cada domicílio, um habitante será selecionado aleatoriamente para ser entrevistado e testado para anticorpos contra SARS-CoV-2, usando o Teste de Anticorpo WONDFO SARS-CoV-2, que foi validado antes do trabalho de campo. Ao avaliar uma amostra representativa dos locais sentinela ao longo do tempo, este estudo fornecerá informações essenciais para o desenho de políticas de saúde.

A Retrospective Survey of Rodent-borne Viruses in Rural Populations of Brazilian Amazon

Abstract INTRODUCTION: The Amazon tropical rainforest has the most dense and diverse ecosystem worldwide. A few studies have addressed rodent-borne diseases as potential hazards to humans in this region. METHODS: A retrospective survey was conducted using enzyme-linked immunosorbent assay for detecting mammarenavirus and orthohantavirus antibodies in 206 samples collected from rural settlers of the Brazilian Western Amazonian region. RESULTS: Six (2.91%) individuals in the age group of 16 to 36 years were found to possess antibodies against mammarenavirus. CONCLUSION: Evidence of previous exposure to mammarenavirus in the rural population points to its silent circulation in this region.

Population-based seroprevalence of SARS-CoV-2 and the herd immunity threshold in Maranhão

ABSTRACT OBJECTIVE: To estimate the seroprevalence of SARS-CoV-2 in the state of Maranhão, Brazil. METHODS: A population-based household survey was performed, from July 27, 2020 to August 8, 2020. The estimates considered clustering, stratification and non-response. Qualitative detection of IgM and IgG antibodies was performed in a fully-automated Elecsys® Anti-SARS-CoV-2 electrochemiluminescence immunoassay on the Cobas® e601 analyzer (Roche Diagnostics). RESULTS: In total, 3,156 individuals were interviewed. Seroprevalence of total antibodies against SARS-CoV-2 was 40.4% (95%CI 35.6-45.3). Population adherence to non-pharmaceutical interventions was higher at the beginning of the pandemic than in the last month. SARS-CoV-2 infection rates were significantly lower among mask wearers and among those who maintained social and physical distancing in the last month compared to their counterparts. Among the infected, 26.0% were asymptomatic. The infection fatality rate (IFR) was 0.14%, higher for men and older adults. The IFR based on excess deaths was 0.28%. The ratio of estimated infections to reported cases was 22.2. CONCLUSIONS: To the best of our knowledge, the seroprevalence of SARS-CoV-2 estimated in this population-based survey is one of the highest reported. The local herd immunity threshold may have been reached or might be reached soon.

Seroprevalence of varicella antibodies in adults without clinical history of disease / Soroprevalência de anticorpos antivaricela em adultos sem história clínica da doença / Seroprevalencia de anticuerpos frente a la varicela en adultos sin historial clínico de la enfermedad

Abstract: Varicella in adults and immunocompromised patients can be severe. The clinical diagnosis of varicella has high accuracy and the history of disease has a high positive predictive value for protection. A significant portion of adults, however, cannot remember if they have had varicella, especially older individuals. We conducted a cross-sectional study to determine the seroprevalence of varicella protective antibodies titers in adults with no clinical history of disease, attended at a Reference Center for Special Immunobiologicals and Travel Medicine in Rio de Janeiro (Brazil). Titration of immunoglobulin G (IgG) antibodies to varicella-zoster was determined by chemiluminescence immunoassay. Among 140 adults without history of varicella, 92% had protective antibody titers. We concluded that seroprevalence of varicella-zoster protection was very high in adults with negative history of disease and the use of serology before vaccination reduced significantly unnecessary vaccine and immunoglobulin use.

Resumo: A varicela é uma doença potencialmente grave em adultos e em pacientes imunocomprometidos. O diagnóstico clínico da varicela apresenta alta acurácia, e o relato da doença na história individual tem alto valor preditivo positivo para a proteção. Entretanto, uma proporção significativa de adultos, principalmente os mais idosos, não se lembra se já teve a doença. Realizamos um estudo transversal para determinar a soroprevalência de títulos protetores de anticorpos contra a varicela em adultos sem história clínica da doença, atendidos em um Centro de Referência para Imunobiológicos Especiais e Medicina de Viagem no Rio de Janeiro, Brasil. Os títulos da imunoglobulina G (IgG) contra varicela-zoster foram determinados por quimiluminescência. Entre 140 adultos sem história de varicela, 92% apresentaram títulos protetores de anticorpos. Concluímos que a soroprevalência de proteção contra varicela-zoster é muito alta em adultos sem história da doença, e que o uso de teste sorológico antes da vacinação reduziria significativamente a vacinação desnecessária e o uso de imunoglobulina.

Resumen: La varicela en adultos y pacientes inmunocomprometidos puede ser grave. El diagnóstico clínico de la varicela tiene una gran precisión y la historia de la enfermedad cuenta con un alto valor predictivo positivo para la protección contra ella. Sin embargo, un porcentaje significativo de adultos, no puede recordar si tuvieron varicela, especialmente las personas más viejas. Realizamos un estudio transversal para determinar la seroprevalencia de las concentraciones de anticuerpos protectores frente a la varicela, en adultos sin historia clínica de la enfermedad, que se llevó a cabo en un Centro de Referencia para Inmunobiología Especial y Medicina del Viajero en Río de Janeiro (Brasil). Se determinó la valoración de los anticuerpos de inmunoglobulina G (IgG) a la varicela-zoster mediante un ensayo inmunológico quimioluminiscente. Entre 140 adultos sin historial de varicela, un 92% tuvieron concentraciones de anticuerpos protectores. Concluimos que la seroprevalencia de la protección a la varicela-zoster fue muy alta en adultos con un historial negativo de la enfermedad y la utilización de la serología antes de la vacunación redujo de manera significativa la vacunación innecesaria y el uso de la inmunoglobulina.

Seroprevalence of cytomegalovirus and its coinfection with Epstein-Barr virus in adult residents from Manaus: a population-based study

Abstract INTRODUCTION: This study assessed the seroprevalence of cytomegalovirus, associated factors, and Epstein-Barr virus coinfection among adult residents of Manaus. METHODS: Using a cross-sectional study design, we collected blood samples from 136 individuals in a household survey in 2016. Prevalence ratios were calculated using Poisson regression. RESULTS: Cytomegalovirus and Epstein-Barr virus seroprevalences were 67.6% (95% CI: 9.7-75.6%) and 97.8% (95% CI: 95.3-100.0%), respectively. Coinfection was observed in 66.2% (95% CI: 58.1-74.2%) of participants. Bivariate analysis showed no statistical association. CONCLUSIONS: Seroprevalences were high among participants and approximately 7 out of 10 individuals had cytomegalovirus and Epstein-Barr virus coinfection.

Seroprevalence of arenavirus and hantavirus in indigenous populations from the Caribbean, Colombia

Abstract INTRODUCTION: In Colombia, there is insufficient epidemiological surveillance of zoonotic hemorrhagic viruses. METHODS: We performed a sero-epidemiological study in indigenous populations of Wayuü, Kankuamos, and Tuchin communities using Maciel hantavirus and Junin arenavirus antigens for IgG detection by ELISA. RESULTS IgG antibodies to hantavirus and arenavirus were found in 5/506 (1%) and 2/506 (0.4%) serum samples, respectively. CONCLUSIONS: Arenavirus and hantavirus circulate in indigenous populations from the Colombian Caribbean region, and the results indicate that the indigenous populations are exposed to these zoonotic agents, with unknown consequences on their health, despite low seroprevalence.

Evolução da prevalência de infecção por COVID-19 no Rio Grande do Sul, Brasil: inquéritos sorológicos seriados / Trends in the prevalence of COVID-19 infection in Rio Grande do Sul, Brazil: repeated serological surveys

Resumo A COVID-19 é uma doença produzida pelo vírus SARS-CoV-2. Esse vírus se espalhou rapidamente pelo mundo, o que levou a Organização Mundial da Saúde a classificar a COVID-19 como uma emergência de saúde internacional e, posteriormente, a declará-la uma pandemia. O número de casos confirmados, no dia 11 de abril de 2020, já passa de 1.700.000, porém esses dados não refletem a real prevalência de COVID-19 na população, visto que, em muitos países, os testes são quase que exclusivamente realizados em pessoas com sintomas, especialmente os mais graves. Para definir políticas de enfrentamento, é essencial dispor de dados sobre a prevalência real de infecção na população. Este estudo tem por objetivos avaliar a proporção de indivíduos já infectados pelo SARS-CoV-2 no Rio Grande do Sul, Brasil, analisar a velocidade de expansão da infecção e estimar o percentual de infectados com e sem sintomas. Serão realizados quatro inquéritos sorológicos repetidos a cada 15 dias, com amostragem probabilística de nove cidades sentinela, em todas as sub-regiões do Estado. As entrevistas e testes ocorrerão no âmbito domiciliar. Serão utilizados testes rápidos para detecção de anticorpos, validados previamente ao início da coleta de dados.

Abstract COVID-19, the disease produced by the virus SARS-CoV-2, has spread quickly throughout the world, leading the World Health Organization to first classify it as an international health emergency and, subsequently, declaring it pandemic. The number of confirmed cases, as April 11, surpassed 1,700,000, but this figure does not reflect the prevalence of COVID-19 in the population as, in many countries, tests are almost exclusively performed in people with symptoms, particularly severe cases. To properly assess the magnitude of the problem and to contribute to the design of evidence-based policies for fighting COVID-19, one must accurately estimate the population prevalence of infection. Our study is aimed at estimating the prevalence of infected individuals in the state of Rio Grande do Sul, Brazil, to document how fast the infection spreads, and to estimate the proportion of infected persons who present or presented symptoms, as well as the proportion of asymptomatic infections. Four repeated serological surveys will be conducted in probability samples of nine sentinel cities every two weeks. Tests will be performed in 4,500 participants in each survey, totaling18,000 interviews. Interviews and tests will be conducted at the participants' household. A rapid test for the detection of antibodies will be used; the test was validated prior to the beginning of the fieldwork.

Dengue diagnostics: serious inaccuracies are likely to occur if pre-analytical conditions are not strictly followed

BACKGROUND The heat-labile nature of Dengue virus (DENV) in serum samples must be considered when applying routine diagnostic tests to avoid issues that could impact the accuracy of test results with direct implications for case management and disease reporting. OBJECTIVES To check if pre-analytical variables, such as storage time and temperature, have an impact on the accuracy of the main routine diagnostic tests for dengue. METHODS Virus isolation, reverse transcription real-time polymerase chain reaction (RT-PCR) and NS1 enzyme-linked immunosorbent assay (ELISA) were evaluated using 84 samples submitted to different pre-analytical conditions. FINDINGS Sensitivity and negative predictive value were directly affected by sample storage conditions. RT-PCR and virus isolation showed greater dependence on well-conserved samples for an accurate diagnosis. Interestingly, even storage at -30ºC for a relatively short time (15 days) was not adequate for accurate results using virus isolation and RT-PCR tests. On the other hand, NS1 ELISA showed no significant reduction in positivity for aliquots tested under the same conditions as in the previous tests. MAIN CONCLUSIONS Our results support the stability of the NS1 marker in ELISA diagnosis and indicate that the accuracy of routine tests such as virus isolation and RT-PCR is significantly affected by inadequate transport and storage conditions of serum samples.

Seroprevalence of anti-SARS-CoV-2 among blood donors in Rio de Janeiro, Brazil

ABSTRACT OBJECTIVE To estimate the seroprevalence of antibodies to SARS-CoV-2 among blood donors in the state of Rio de Janeiro, Brazil. METHODS Data were collected on 2,857 blood donors from April 14 to 27, 2020. This study reports crude prevalence of antibodies to SARS-CoV-2, population weighted prevalence for the state, and prevalence adjusted for test sensitivity and specificity. Logistic regression models were used to establish the correlates of SARS-CoV-2 prevalence. For the analysis, we considered collection period and site, sociodemographic characteristics, and place of residence. RESULTS The proportion of positive tests for SARS-Cov-2, without any adjustment, was 4.0% (95%CI 3.3-4.7%), and the weighted prevalence was 3.8% (95%CI 3.1-4.5%). We found lower estimates after adjusting for test sensitivity and specificity: 3.6% (95%CI 2.7-4.4%) for the non-weighted prevalence, and 3.3% (95%CI 2.6-4.1%) for the weighted prevalence. Collection period was the variable most significantly associated with crude prevalence: the later the period, the higher the prevalence. Regarding sociodemographic characteristics, the younger the blood donor, the higher the prevalence, and the lower the education level, the higher the odds of testing positive for SARS-Cov-2 antibody. We found similar results for weighted prevalence. CONCLUSIONS Our findings comply with some basic premises: the increasing trend over time, as the epidemic curve in the state is still on the rise; and the higher prevalence among both the youngest, for moving around more than older age groups, and the less educated, for encountering more difficulties in following social distancing recommendations. Despite the study limitations, we may infer that Rio de Janeiro is far from reaching the required levels of herd immunity against SARS-CoV-2.