ABSTRACT
Community testing is a crucial tool for the early identification of SARS-CoV-2 infection and transmission control. The emergence of the highly mutated Omicron variant (B.1.1.259) raised concerns about its primary site of replication, impacting sample collection, and its detectability by rapid antigens tests. We tested the Antigen Rapid Diagnostic Test (Ag-RDT) performance using nasal, oral, and saliva specimens for COVID-19 diagnosis in 192 symptomatic individuals, using RT-qPCR from nasopharyngeal samples as control. Variant of Concern (VOC) investigation was determined by the 4Plex SARS-CoV-2 screening kit. SARS-CoV-2 positivity rate was 66.2%, with 99% of the positive samples showing an amplification profile consistent with that of the Omicron variant. Nasal Ag-RDT showed higher sensitivity (89%) than oral (12.6%) and saliva (22.1%) Ag-RDTs. Our data showed the good performance of the Ag-RDT in a pandemic scenario dominated by the Omicron VOC. Furthermore, our data also demonstrated that nasal specimens perform better than oral and saliva ones for Omicron Ag-RDT detection.
Subject(s)
COVID-19ABSTRACT
The emergence and widespread circulation of SARS-CoV-2 variants of concern (VOC) or interest (VOI) imposes an enhanced threat to global public health. In Brazil, one of the countries most severely impacted throughout the pandemic, a complex dynamics involving variants co-circulation and turnover events has been recorded with the emergence and spread of VOC Gamma in Manaus in late 2020. In this context, we present a genomic epidemiology investigation based on samples collected between December 2020 and May 2021 in the second major Brazilian metropolis, Rio de Janeiro. By sequencing 244 novel genomes through all epidemiological weeks in this period, we were able to document the introduction and rapid dissemination of VOC Gamma in the city, driving the rise of the third local epidemic wave. Molecular clock analysis indicates this variant has circulated locally since the first weeks of 2021 and only seven weeks were necessary for it to achieve a frequency above 70%, consistent with rates of growth observed in Manaus and other states. Moreover, a Bayesian phylogeographic reconstruction indicates VOC Gamma spread throughout Brazil between December 2020 and January 2021, and that it was introduced in Rio de Janeiro through at least 13 events coming from nearly all regions of the country. Comparative analysis of RT-qPCR cycle threshold (Ct) values provide further evidence that VOC Gamma induces higher viral loads (N1 target; mean reduction of Ct: 2.7, 95% CI = 2.0 - 3.4). This analysis corroborates the previously proposed mechanistic basis for this variant enhanced transmissibility and distinguished epidemiological behavior. Our results document the evolution of VOC Gamma and provide independent assessment of scenarios previously studied in Manaus, therefore contributing to the better understanding of the epidemiological dynamics currently being surveyed in other Brazilian regions.
ABSTRACT
Background: During the COVID-19 pandemic, olfactory dysfunction (anosmia or hyposmia) has been reported by many patients and recognized as a prevalent and early symptom of infection. This finding has been associated with viral-induced olfactory neuron dysfunction rather than the nasal congestion typically found in cold- or flu-like states. In literature, the prevalence of anosmia varies from 15% to 85%, and the studies, in general, were based on the subjective evaluation of patients' self-reports of loss of smell (yes or no question). In the present study, we quantitatively evaluated olfactory dysfunction and the prevalence of fever in symptomatic patients suspected of having COVID-19 using a scratch-and-sniff olfactory test and infrared temperature testing with Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) as the gold&-standard comparator method to diagnose COVID-19 infection. Methods: Outpatients had their forehead temperature checked with an infrared non-contact thermometer (temperature guns). After that, they received two olfactory smell identification test (SIT) cards (u-Smell-it ; CT, USA) that each had 5 scent windows and were asked to scratch with a pencil and sniff each of the 10 small circles containing the microencapsulated fragrances and mark the best option on a response card. Nasopharyngeal swabs were then collected for Reverse RT-PCR to determine if the patients were positive or negative for COVID-19 infection. We considered the number of 'hits' (correct answers) [≤] 5 as positive for loss of smell (LOS) in the olfactory test; [≥] 6 hits was considered negative for LOS (i.e. normal olfactory function). All data were analyzed using Excel and Matlab software. Results: In the present study, 165 patients were eligible for the olfactory test and nasopharyngeal swab collection RT-PCR. Five patients were excluded because of inconclusive PCR results (n=2) and missing data (n=3). A total of 160 patients completed all the protocols. The RT-PCR positivity rate for COVID-19 was 27.5% (n=44), and PCR+ patients scored significantly worse in the olfactory test (5.5{+/-}3.5) compared to RT-PCR- patients (8.2{+/-}1.8, p<0.001). 0/44 PCR+ patients presented with a fever ([≥]37.8{degrees}C). In contrast an olfactory SIT had a specificity of 94.8% (95% CI, 89.1 - 98.1), sensitivity of 47.7% (95% CI, 32.7 - 63.3), accuracy of 0.82 (95% CI, 0.75 - 0.87), positive predictive value of 77.8% (95% CI, 59.6 - 88.8), negative predictive value of 82.7% (85% CI, 78.7 - 86.7), and odds ratio of 16.7. Conclusion: Our results suggest that temperature checking failed to detect COVID-19 infection, while an olfactory test may be useful to help identify COVID-19 infection in symptomatic patients.