Moist heat as a promising method to decontaminate N95 masks: A large scale clinical study comparing four decontamination modalities-moist heat, steam, ultraviolet-C irradiation, and hydrogen peroxide plasma.

BACKGROUND: Early in the COVID-19 pandemic, there was a global shortage of masks. Although mask reprocessing was practiced, no clinical study has assessed systematically the impact of repeated cycles of wear and decontamination on the integrity of N95 filtering facepiece respirators (FFRs). METHODS: We evaluated mask fit assessed by qualitative respirator fit test (QRFT) after each cycle of wear and decontamination, as well as four measures of mask integrity-bacterial filtration efficacy, particle filtration efficacy, differential pressure, and splash resistance through five cycles of wear and decontamination using one of the four modalities (moist heat, steam, ultraviolet-C irradiation, and hydrogen peroxide plasma). RESULTS: A total of 60.6% (hydrogen peroxide plasma) to 77.5% (moist heat) of the FFRs passed five cycles of wear and decontamination, as assessed by the wearers passing QRFT all five times. Moist heat-decontaminated FFRs retained all technical measures of integrity through all five cycles. CONCLUSIONS: This is the first large-scale study to assess systematically the impact (clinically and quantitatively) on N95 FFR integrity of repeated cycles of wearing followed by decontamination. Our results suggest that moist heat is a promising method for decontaminating N95 FFRs. Performing QRFT after every cycle of wear and decontamination ensures wearer safety. Although there is currently no mask shortage, reprocessing may reduce medical waste and improve sustainability.

Detection of viable SARS-CoV-2 in deep respiratory specimens despite negative nasopharyngeal SARS-CoV-2 RT-PCR: Occult COVID-19 as an unsuspected cause of pulmonary infiltrates in immunocompromised patients.

Background: Prolonged shedding/relapse of COVID-19 infection has been reported, particularly in patients who received anti-CD20 agents (eg. rituximab). However, cases of occult COVID-19, in which SARS-CoV-2 persistence in lung parenchyma is diagnosed despite clearance from nasopharyngeal (NP) specimens, are uncommon. Case summary: We describe two cases of occult COVID-19 in immunocompromised patients. Both patients had received rituximab previously. Both cases initially presented as ground-glass infiltrates on lung imaging; the diagnosis was originally not suspected due to repeated demonstration of negative SARS-CoV-2 from NP specimens, and alternative etiologies were originally considered. Persistence of SARS-CoV-2 in lung parenchyma, however, was demonstrated on bronchoalveolar lavage (BAL) specimens; additionally, isolation of viable SARS-CoV-2 virus and detection of SARS-CoV-2 nucleocapsid and spike-protein antigen in lung tissue on immunohistochemistry close to 3-months from primary infection strongly suggested ongoing viral persistence and replication as a driver of the lung parenchymal changes, which resolved after antiviral treatment. Discussion: Occult COVID-19 can be a cause of unexplained ground-glass infiltrates on lung imaging; negative NP samples do not rule out SARS-CoV-2 persistence and invasive sampling must be considered. The unsuspected presence of viable virus on BAL, however, highlights that procedurists perfoming aerosol-generating-procedures during an ongoing pandemic wave must also practise appropriate infection-prevention precautions to limit potential exposure.

Favorable vaccine-induced SARS-CoV-2-specific T cell response profile in patients undergoing immune-modifying therapies.

BACKGROUNDPatients undergoing immune-modifying therapies demonstrate a reduced humoral response after COVID-19 vaccination, but we lack a proper evaluation of the effect of such therapies on vaccine-induced T cell responses.METHODSWe longitudinally characterized humoral and spike-specific T cell responses in patients with inflammatory bowel disease (IBD), who were on antimetabolite therapy (azathioprine or methotrexate), TNF inhibitors, and/or other biologic treatment (anti-integrin or anti-p40) for up to 6 months after completing 2-dose COVID-19 mRNA vaccination.RESULTSWe demonstrate that a spike-specific T cell response was not only induced in treated patients with IBD at levels similar to those of healthy individuals, but also sustained at higher magnitude for up to 6 months after vaccination, particularly in those treated with TNF inhibitor therapy. Furthermore, the spike-specific T cell response in these patients was mainly preserved against mutations present in SARS-CoV-2 B.1.1.529 (Omicron) and characterized by a Th1/IL-10 cytokine profile.CONCLUSIONDespite the humoral response defects, patients under immune-modifying therapies demonstrated a favorable profile of vaccine-induced T cell responses that might still provide a layer of COVID-19 protection.FUNDINGThis study was funded by the National Centre for Infectious Diseases (NCID) Catalyst Grant (FY2021ES) and the National Research Fund Competitive Research Programme (NRF-CRP25-2020-0003).

Exploring Reusability of Disposable Face Masks: Effects of Disinfection Methods on Filtration Efficiency, Breathability, and Fluid Resistance.

To curb the spread of the COVID-19 virus, the use of face masks such as disposable surgical masks and N95 respirators is being encouraged and even enforced in some countries. The widespread use of masks has resulted in global shortages and individuals are reusing them. This calls for proper disinfection of the masks while retaining their protective capability. In this study, the killing efficiency of ultraviolet-C (UV-C) irradiation, dry heat, and steam sterilization against bacteria (Staphylococcus aureus), fungi (Candida albicans), and nonpathogenic virus (Salmonella virus P22) is investigated. UV-C irradiation for 10 min in a commercial UV sterilizer effectively disinfects surgical masks. N95 respirators require dry heat at 100 °C for hours while steam treatment works within 5 min. To address the question on safe reuse of the disinfected masks, their bacteria filtration efficiency, particle filtration efficiency, breathability, and fluid resistance are assessed. These performance factors are unaffected after 5 cycles of steam (10 min per cycle) and 10 cycles of dry heat at 100 °C (40 min per cycle) for N95 respirators, and 10 cycles of UV-C irradiation for surgical masks (10 min per side per cycle). These findings provide insights into formulating the standard procedures for reusing masks without compromising their protective ability.

Widely heterogeneous humoral and cellular immunity after mild SARS-CoV-2 infection in a homogeneous population of healthy young men.

BACKGROUND: We studied humoral and cellular responses against SARS-CoV-2 longitudinally in a homogeneous population of healthy young/middle-aged men of South Asian ethnicity with mild COVID-19. METHODS: In total, we recruited 994 men (median age: 34 years) post-COVID-19 diagnosis. Repeated cross-sectional surveys were conducted between May 2020 and January 2021 at six time points - day 28 (n = 327), day 80 (n = 202), day 105 (n = 294), day 140 (n = 172), day 180 (n = 758), and day 280 (n = 311). Three commercial assays were used to detect anti-nucleoprotein (NP) and neutralizing antibodies. T cell response specific for Spike, Membrane and NP SARS-CoV-2 proteins was tested in 85 patients at day 105, 180, and 280. RESULTS: All serological tests displayed different kinetics of progressive antibody reduction while the frequency of T cells specific for different structural SARS-CoV-2 proteins was stable over time. Both showed a marked heterogeneity of magnitude among the studied cohort. Comparatively, cellular responses lasted longer than humoral responses and were still detectable nine months after infection in the individuals who lost antibody detection. Correlation between T cell frequencies and all antibodies was lost over time. CONCLUSION: Humoral and cellular immunity against SARS-CoV-2 is induced with differing kinetics of persistence in those with mild disease. The magnitude of T cells and antibodies is highly heterogeneous in a homogeneous study population. These observations have implications for COVID-19 surveillance, vaccination strategies, and post-pandemic planning.

Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection.

The efficacy of virus-specific T cells in clearing pathogens involves a fine balance between antiviral and inflammatory features. SARS-CoV-2-specific T cells in individuals who clear SARS-CoV-2 without symptoms could reveal nonpathological yet protective characteristics. We longitudinally studied SARS-CoV-2-specific T cells in a cohort of asymptomatic (n = 85) and symptomatic (n = 75) COVID-19 patients after seroconversion. We quantified T cells reactive to structural proteins (M, NP, and Spike) using ELISpot and cytokine secretion in whole blood. Frequencies of SARS-CoV-2-specific T cells were similar between asymptomatic and symptomatic individuals, but the former showed an increased IFN-γ and IL-2 production. This was associated with a proportional secretion of IL-10 and proinflammatory cytokines (IL-6, TNF-α, and IL-1ß) only in asymptomatic infection, while a disproportionate secretion of inflammatory cytokines was triggered by SARS-CoV-2-specific T cell activation in symptomatic individuals. Thus, asymptomatic SARS-CoV-2-infected individuals are not characterized by weak antiviral immunity; on the contrary, they mount a highly functional virus-specific cellular immune response.

Experience of a Tertiary Hospital in Singapore with Management of a Dual Outbreak of COVID-19 and Dengue.

During the COVID-19 pandemic, distinguishing dengue from cases of COVID-19 in endemic areas can be difficult. In a tertiary hospital contending with COVID-19 during a dengue epidemic, a triage strategy of routine COVID-19 testing for febrile patients with viral prodromes was used. All febrile patients with viral prodromes and no epidemiologic risk for COVID-19 were first admitted to a designated ward for COVID-19 testing, where enhanced personal protective equipment was used by healthcare workers until COVID-19 was ruled out. From January to May 2020, 11,086 admissions were screened for COVID-19; 868 cases of COVID-19 were diagnosed in our institution, along with 380 cases of dengue. Only 8.5% (943/11,086) of suspected COVID-19 cases were concurrently tested for dengue serology due to a compatible overlapping clinical syndrome, and dengue was established as an alternative diagnosis in 2% (207/10,218) of suspected COVID-19 cases that tested negative. There were eight COVID-19 cases with likely false-positive dengue serology and one probable COVID-19/dengue coinfection. From April to May 2020, 251 admissions presenting as viral prodromes with no respiratory symptoms were screened; of those, 15 cases had COVID-19, and 2/15 had false-positive dengue IgM. Epidemiology investigations showed no healthcare-associated transmission. In a dengue epidemic season coinciding with a COVID-19 pandemic, dengue was established as an alternative diagnosis in a minority of COVID-19 suspects, likely due to early availability of basic diagnostics. Routine screening of patients with viral prodromes during a dual outbreak of COVID-19 and dengue enabled containment of COVID-19 cases masquerading as dengue with false-positive IgM.

Bilateral psoas abscess caused by Janibacter terrae, an unusual condition and organism resulting in laboratory and management conundrums.

Psoas abscess is commonly regarded as an unusual cause for back pains and usually associated with significant risk factors or co-morbidities. We describe the clinical presentation and findings of a young male Caucasian with bilateral psoas abscesses caused by an unusual organism, Janibacter terrae (an environmental organism) not previously described in literature and the challenges faced in managing this infection. There are very few case reports of this organism causing opportunistic infections, all reported bacteraemia mainly in patients with significant co-morbidities. This case highlights the importance of psoas abscess as a differential diagnosis in patients presenting with back pain and the potential for this organism to cause abscesses in healthy individuals which was difficult to identify using conventional laboratory methods. Management of this infection was challenging and there is limited experience with antimicrobial treatment for this organism.