Background: In Brazil, mathematical models for deriving estimates and projections of COVID-19 cases have been developed without data on asymptomatic SARS-CoV-2 infection. We estimated the seroprevalence of antibodies to SARS-CoV-2 among blood donors in the State of Rio de Janeiro. Methods: Data were collected on 2,857 blood donors from April 14 to 27, 2020. We report the crude prevalence of antibodies to SARS-CoV-2, the weighted prevalence by the total state population, and adjusted prevalence estimates for test sensitivity and specificity. To establish the correlates of SARS-CoV-2 prevalence, we used logistic regression models. The analysis included period and site of blood collection, sociodemographic characteristics, and place of residence. Results: The proportion of SARS-Cov-2 positive tests 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%). Further adjustment by test sensitivity and specificity produced lower estimates, 3.6% (95% CI 2.7-4.4%) and 3.3% (95% CI 2.6-4.1%), respectively. The variable most significantly associated with the crude prevalence was the period of blood collection: the later the period, the higher the prevalence. Regarding socio-demographic characteristics, the younger the blood donors, the higher the prevalence, and the lower the educational level, the higher the odds of a positive SARS-Cov-2 antibody. Similar results were found for the weighted prevalence. Discussion: Although our findings resulted from a convenience sample, they match some basic premises: the increasing trend over time, since the epidemic curve in the state is still on the rise; the higher prevalence among the youngest who are more likely to circulate; and the higher prevalence among the less educated as they have more difficulties in following the social distancing recommendations. Despite the study limitations, it is possible to infer that protective levels of natural herd immunity to SARS-CoV-2 are far from being reached in Rio de Janeiro.

The molecular prevalence of human parvovirus B19V (B19V) in bone marrow (BM) samples from 120 cases with cytopenias of unknown etiology was compared with that in samples from 45 BM donors (control group 1) and 120 oncohematological patients (control group 2) to determine the role that B19V genotypes may play in unexplained cytopenias. Of the 285 participants, the BM samples of 39 (13.7%) contained B19V DNA (21 with genotype 1, 5 with genotype 2, and 13 with genotype 3). The prevalences of B19V were similar between case and control subjects (15.0% versus 12.7%, respectively). Genotypes 2 and 3 were associated with older age and were detected in similar proportions between case and control group 2 subjects. The results of this study do not support a role for B19V genotype variants in the etiology of unexplained cytopenias.Human parvovirus B19 (B19V), which belongs to the genus Erythrovirus of the family Parvoviridae, is a tiny single-stranded DNA virus that propagates in actively dividing erythroid lineage progenitors of bone marrow (BM) and blood, inhibiting erythropoiesis (1). Comparisons of B19V genomic sequences from different isolates identified 3 genetically distinct B19V genotypes with more than 10% genetic variability among them. These were designated genotype 1 (B19-related viruses), genotype 2 (A6-related viruses), and genotype 3 (V9-related viruses) (5). Infection with B19V genotype 1 has been associated with a wide range of human diseases, including erythema infectiosum, arthropathy, transient aplastic crisis, persistent anemia, and hydrops fetalis (6).We have previously shown that genotype 3 accounts for approximately 50% of the parvovirus-positive samples in our center (4); however, the clinical significance of this finding has not yet been determined. In this study, we aimed to determine if the presence of B19V genotypes 2 and 3 isolated from BM cells is associated with cytopenias of unknown etiology.An unmatched 1:2 case-control study was conducted from September 2006 to May 2009. Based on the results of our previous study and on the following assumptions (␣ ϭ 0.05; power ϭ 0 to 80; prevalence rate of B19V in patients ϭ 17.5%; odds ratio for B19V infection ϭ 2.8; ratio of controls to cases ϭ 2:1), it was determined that a sample size of 122 cases was needed to demonstrate a link between B19V infection and cytopenia. Accordingly, for this study, we recruited a total of 120 cases fulfilling the recommended diagnostic criteria for idiopathic cytopenia. These criteria define idiopathic cytopenia as cytopenia in one or more cell lineages (i) that persists for at least 6 months and (ii) that cannot be explained by any other hematological or nonhematological disease. Two control groups were chosen to enhance the power of the study. Control group 1 consisted of 45 BM donors, and group 2 included 120 patients with oncohematological disorders (Table 1). We were unable to identify two controls for every case, and the total number of controls was thus limited to 165.Peripheral blood (PB) (5 ml) and BM samples ...

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