Suspected case of monkeypox reinfection versus reactivation in a immunocompetent patient, Barcelona, 2022.

Vaccines against smallpox are known to have cross-protective activity against monkeypox, and smallpox and monkeypox infections are believed to generate permanent immunity. Nevertheless, there are scarce data about the possibility of reinfection or reactivation. Recently, a case of apparent monkeypox reinfection has been reported. We present a suspected case of second episode of monkeypox in a healthy and previously vaccinated man, with a confirmed primary monkeypox infection occurring three months before the second confirmed presentation.

Results from a systematic programme of evaluating COVID-19 reinfection cases in the early phase of the pandemic, Singapore.

OBJECTIVES: The objectives of this study were to describe the coronavirus disease caused by SARS-CoV-2 (COVID-19) reinfection evaluation algorithm used in the early phase of the pandemic in Singapore and analyze the clinical and laboratory characteristics of the cases evaluated. METHODS: We performed a retrospective case-control analysis including all COVID-19 cases evaluated for possible reinfection under the local COVID-19 reinfection evaluation programme between 1 June 2020-30 June 2021. Whole genome sequencing (WGS) was used as confirmatory testing. We compared all reinfection ("RI") cases against those who were evaluated but eventually assessed not to be reinfection ("non-RI"). RESULTS: There were 74 possible reinfection cases evaluated through the programme, of which 32 were subsequently classified as RI. There was strong statistical evidence that RI cases had a longer interval between 1st and 2nd episode (mean 297 days; 95%-confidence interval (CI) 267-327) compared to non-RI cases (mean 186 days; 95%-CI 144-228). The cycle threshold (Ct) value of initial polymerase chain rection (PCR) at 2nd episode was also found to be significantly lower in RI cases (mean 23; 95%-CI 20-26) compared to non-RI cases (mean 34; 95%-CI 32-36). There was no significant difference in the proportion of individuals who had fever, acute respiratory symptoms or asymptomatic in both groups. Delta and beta variants were most commonly identified from WGS and provide indication of re-infection as these were not 'wild-type' and were not circulating during the time period of the index infection. CONCLUSIONS: Using a combination of serologic, microbiologic and genomic criteria to evaluate possible reinfection cases is useful and can provide a framework for evaluation that may be modified for future similar situations.

Distinguishing Severe Acute Respiratory Syndrome Coronavirus 2 Persistence and Reinfection: A Retrospective Cohort Study.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection is poorly understood, partly because few studies have systematically applied genomic analysis to distinguish reinfection from persistent RNA detection related to initial infection. We aimed to evaluate the characteristics of SARS-CoV-2 reinfection and persistent RNA detection using independent genomic, clinical, and laboratory assessments. METHODS: All individuals at a large academic medical center who underwent a SARS-CoV-2 nucleic acid amplification test (NAAT) ≥45 days after an initial positive test, with both tests between 14 March and 30 December 2020, were analyzed for potential reinfection. Inclusion criteria required having ≥2 positive NAATs collected ≥45 days apart with a cycle threshold (Ct) value <35 at repeat testing. For each included subject, likelihood of reinfection was assessed by viral genomic analysis of all available specimens with a Ct value <35, structured Ct trajectory criteria, and case-by-case review by infectious diseases physicians. RESULTS: Among 1569 individuals with repeat SARS-CoV-2 testing ≥45 days after an initial positive NAAT, 65 (4%) met cohort inclusion criteria. Viral genomic analysis characterized mutations present and was successful for 14/65 (22%) subjects. Six subjects had genomically supported reinfection, and 8 subjects had genomically supported persistent RNA detection. Compared to viral genomic analysis, clinical and laboratory assessments correctly distinguished reinfection from persistent RNA detection in 12/14 (86%) subjects but missed 2/6 (33%) genomically supported reinfections. CONCLUSIONS: Despite good overall concordance with viral genomic analysis, clinical and Ct value-based assessments failed to identify 33% of genomically supported reinfections. Scaling-up genomic analysis for clinical use would improve detection of SARS-CoV-2 reinfections.

Retrospective review of re-positive qPCR tests for SARS-CoV: do they indicate presence of reinfection?

OBJECTIVE: In 2019, the Coronavirus Disease 2019 (COVID-19) pandemic broke out, caused by the coronavirus called Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Reinfections can be observed with various respiratory viruses, including human coronaviruses. Moreover, they may result from weak or waning initial immune response, reinfection with another genotype/subtype, or the rapid antigenic changes in the virus. The aim of this study was to investigate the likelihood of reinfection in COVID-19 patients that had a positive qPCR test result at least 60 days after a negative test result in patients that were confirmed with COVID-19 on qPCR. MATERIALS AND METHODS: The quantitative polymerase chain reaction (qPCR) results of a total of 105,000 samples that had been obtained between April 1, 2020, and February 1, 2021, in two separate authorized laboratories were retrospectively analyzed. 22 samples from 11 patients included in the study, qPCR tests were repeated for each sample using the Rotorgene Q PCR system with Diagnovital SARS-CoV-2 (RTA Labs, Turkey) Real-Time PCR kits. Positive samples were screened for B.1.1.7 and E484K mutations using the qPCR method on the Rotorgene Q PCR system with Bio-Speedy SARS-CoV-2 Variant Plus kits (Bioeksen Technology, Turkey). RESULTS: The 105,000 individuals comprised 55,614 men and 49,386 women. In the qPCR test, 14,511 (13.82%) individuals were found to be positive for SARS-CoV-2. Of these, 11 (0.076%) patients were included in the study based on the inclusion criteria. Accordingly, the risk of reinfection was calculated as 0.076% (95% confidence interval [CI]: 0.056%-0.096%) and the incidence was 1.04 per 10,000 population (95% CI: 0.62-1.38 per 10,000). No patient was admitted to the intensive care unit or died during both episodes. Moreover, no B.1.1.7 or E484K mutation was detected in any patient. CONCLUSIONS: The high frequency of COVID-19 infection poses serious risks for the development of new variants and the currently used vaccines are likely to lose their efficacy against new variants. To reduce these risks and to be successful in the fight against the pandemic, we suggest compliance with personal protective measures as well as rapid and widespread application of vaccination not only in developed countries but also in the whole world and the modification of currently used vaccines in such a way to fight against newly emerged variants.

Possible Cases of SARS-CoV-2 Reinfection In Pekanbaru, Indonesia.

Confirmed and possible reinfection cases of SARS-CoV-2 have been reported from various countries. Here we present two cases of possible SARS-CoV-2 reinfection in Pekanbaru, Indonesia. A 26 years old female and a 27 years old male healthcare workers were first confirmed by PCR with high Ct-value (>35) while presenting no or mild symptoms, respectively. In more than one month since the last negative test results, both patients developed typical COVID-19 symptoms; fever and anosmia. RT-PCR results for SARS-CoV-2 were positive with Ct-value less than 30. The timeframe between 1st and 2nd episode, negative test result between episodes, and epidemiological risk factor strengthened the possibility of reinfection. However, we did not have whole genome sequence (WGS) or viral viability data to further confirm reinfection with different viable virus. The requirement of viral WGS data to confirm true reinfection cases calls for investment in whole genome sequencing platform in public health laboratories. We encourage standardized definition of SARS-CoV-2 reinfection case in order to be able to investigate and observe such cases.

Avidity of IgG to SARS-CoV-2 RBD as a Prognostic Factor for the Severity of COVID-19 Reinfection.

The avidity index (AI) of IgG to the RBD of SARS-CoV-2 was determined for 71 patients with a mild (outpatient) course of COVID-19, including 39 primarily and 36 secondarily reinfected, and 92 patients with a severe (hospital) course of COVID-19, including 82 primarily and 10 secondarily infected. The AI was shown to correlate with the severity of repeated disease. In the group of outpatients with a mild course, the reinfected patients had significantly higher median AIs than those with primary infections (82.3% vs. 37.1%, p < 0.0001). At the same time, in patients with a severe course of COVID-19, reinfected patients still had low-avidity antibodies (median AI of 28.4% vs. 25% in the primarily infected, difference not significant, p > 0.05). This suggests that the presence of low-avidity IgG to RBD during reinfection is a negative prognostic factor, in which a patient's risk of developing COVID-19 in a severe form is significantly increased. Thus, patients with IgG of low avidity (AI ≤ 40%) had an 89 ± 20.5% chance of a severe course of recurrent COVID-19, whereas the detection of high-avidity antibodies (AI ≥ 50%) gave a probability of 94 ± 7.9% for a mild course of recurrent disease (p < 0.05).

COVID-19 reinfection after pregnancy.

BACKGROUND: There have been reports of COVID-19 reinfections, but the immunological characterization of these cases is partial. We report a case of reinfection with SARS-CoV-2, where the first infection occurred in the course of late pregnancy. CASE PRESENTATION: On May 27, 2020, a 37-year-old woman gave birth at full term, 3 hours after full dilatation. She developed fever (38.3°C) after delivery. Mild biological anomalies compatible with COVID-19 were observed: lymphopenia, thrombocytopenia, elevated D-Dimers, CRP, and LDH. At 6-month follow-up, she reported having contracted COVID-19 with high fever, rhinorrhea, hand frostbites, cough, headache, dysgeusia and anosmia. CONCLUSIONS: We report a case of COVID-19 reinfection with a first mild infection during late pregnancy and a more aggressive second infection 5 months later.

COVID-19 reinfections among naturally infected and vaccinated individuals.

The protection against emerging SARS-CoV-2 variants by pre-existing antibodies elicited due to the current vaccination or natural infection is a global concern. We aimed to investigate the rate of SARS-CoV-2 infection and its clinical features among infection-naïve, infected, vaccinated, and post-infection-vaccinated individuals. A cohort was designed among icddr,b staff registered for COVID-19 testing by real-time reverse transcriptase-polymerase chain reaction (rRT-PCR). Reinfection cases were confirmed by whole-genome sequencing. From 19 March 2020 to 31 March 2021, 1644 (mean age, 38.4 years and 57% male) participants were enrolled; where 1080 (65.7%) were tested negative and added to the negative cohort. The positive cohort included 750 positive patients (564 from baseline and 186 from negative cohort follow-up), of whom 27.6% were hospitalized and 2.5% died. Among hospitalized patients, 45.9% had severe to critical disease and 42.5% required oxygen support. Hypertension and diabetes mellitus were found significantly higher among the hospitalised patients compared to out-patients; risk ratio 1.3 and 1.6 respectively. The risk of infection among positive cohort was 80.2% lower than negative cohort (95% CI 72.6-85.7%; p < 0.001). Genome sequences showed that genetically distinct SARS-CoV-2 strains were responsible for reinfections. Naturally infected populations were less likely to be reinfected by SARS-CoV-2 than the infection-naïve and vaccinated individuals. Although, reinfected individuals did not suffer severe disease, a remarkable proportion of naturally infected or vaccinated individuals were (re)-infected by the emerging variants.

Situación en la realización de pruebas diagnósticas para SARS-CoV-2 (COVID-19) ante nueva variante Ómicron (B. 1. 1. 529) / Situation in the performance of diagnostic tests for SARS-CoV-2 (COVID-19) in the face of the new Ómicron variant (B. 1. 1. 529)

INTRODUCCIÓN: El virus SARS-CoV-2, con el tiempo ha mutado y sigue presentando múltiples variantes, lo que ha dado lugar a una variación genética en la población de cepas virales circulantes en el transcurso de la pandemia de COVID-19. La Organización Mundial de la Salud (OMS) ha estandarizado dichas variantes según el interés y preocupación que ocasionan. El espectro de la enfermedad es amplio e incluye desde cuadros leves y autolimitados hasta neumonía atípica severa y progresiva, falla multiorgánica y muerte. Se detecta en la saliva de pacientes con enfermedad por coronavirus (COVID-19) ha sido que este fluido biológico fuera relevante en términos del diagnóstico y transmisión de la infección. Se cree que el virus se replica en la nariz y la garganta, como se evidencia por la alta carga viral en la etapa temprana de infección en estas áreas. La Organización Mundial de la Salud (OMS), el 26 de noviembre de 2021, designó al nuevo linaje B.1.1.529 del virus SARS-CoV-2 como Variante de Preocupación (VOC) para la salud pública, asignando el nombre según el alfabeto griego, Ómicron. Esta variante tiene significativamente más mutaciones que las variantes anteriores de SARS-CoV-2, por lo que es más transmisible, es decir se propaga con mayor facilidad. El incremento considerable de la detección de casos sospechosos de la variante B.1.1.529, ha llevado a OMS a tomar la decisión de designarla como una variante de preocupación como una medida de precaución. En medida de este contexto de la variante Ómicron los equipos de respuesta de los laboratorios de la OPS/OMS recomiendan las pruebas de laboratorio para diagnóstico de SARS-CoV-2 como diagnóstico molecular (RT-PCR en tiempo real) y diagnóstico por detección de Antígeno (Pruebas rápidas de antígeno, Ag-RDT). OBJETIVO: El objetivo del presente informe es describir la alta demanda de la realización de las pruebas diagnósticas para SARS-CoV-2 ante la nueva variante Ómicron (B.1.1.529) del SARS-CoV-2. METODOLOGÍA: Se efectuó una búsqueda electrónica en las páginas oficiales de las principales agencias gubernamentales de la región sobre el proceso de realización de las pruebas diagnósticas para SARS-CoV-2 ante la nueva variante Ómicron. La búsqueda fue limitada a documentos desarrollados en idioma español o inglés, sin restricción por fecha de publicación. La selección de las publicaciones se realizó a partir de la lectura de título y resumen, así como la selección a partir de la lectura de texto completo fue efectuada por un solo revisor. RESULTADOS: En cuanto a las recomendaciones sobre la realización de pruebas diagnósticas para el SARS-CoV-2 ante la nueva variante Ómicron, encontramos lo siguiente: Agencias Internacionales: OMS: La OMS recomienda a los estados miembros mejorar la vigilancia con pruebas rápidas (antigénicas), investigación rigurosa de conglomerados y rastreo de contactos sospechosos de ser infectados con la variante Ómicron. Adicionalmente, recomienda que las capacidad nacional de testeo y secuenciación genómica deben ser adecuadamente planificados por posibles incrementos en la demanda de pruebas diagnósticas. OPS: La OPS recomienda mantener los protocolos ya implementados de rutina para la detección molecular de SARS-CoV-2; también recomienda mantener el uso rutinario de las pruebas rápidas de antígeno según los protocolos de cada país [2]. Además, con el fin de mejorar la vigilancia genómica, la OPS recomienda incrementar la secuenciación con envío de muestras a los laboratorios de referencia de secuenciación de la Red Regional de Vigilancia Genómica de COVID-19 de la OPS/OMS (COVIGEN) y mantener o aumentar las capacidades en aquellos laboratorios que tienen plataformas de secuenciación ya implementadas [2]. Por otro lado, en la alerta epidemiológica del 10 de enero de 2022, la OPS recomienda el uso racional de pruebas diagnósticas frente al incremento acelerado de casos en varios países de Europa y América y el aumento abrupto del consumo de pruebas diagnósticas. Las recomendaciones comprenden criterios de priorización para el uso de pruebas de COVID-19, tanto antigénicas y moleculares, y son las siguientes: 1) todos los casos con indicación de hospitalización por síntomas respiratorios; 2) profesionales de la salud con síntomas respiratorios; 3) detección en pacientes que necesitan ser hospitalizados por otras razones según normativa de cada país; 4) profesionales con síntomas respiratorios que forman parte de servicios esenciales y presenciales. CDC: La CDC, junto a los laboratorios de salud pública de Estados Unidos y la Asociación de Laboratorios de Salud Pública, está implementando una vigilancia mejorada de especímenes con falla de detección del gen S (sospechoso de la variante Ómicron). La CDC solicita a los laboratorios de salud pública que le envíen los especímenes sospechosos lo más pronto posible para la confirmación del posible caso de variante Ómicron y consiguiente caracterización virológica [4]. De esta manera, Estados Unidos tiene un sistema de vigilancia mejorada y multifacética para detectar las variantes circulantes en el país. Este sistema obtiene datos de vigilancia genómica provenientes de 1) Vigilancia Nacional de Cepas de SARS-CoV-2; 2) Contratos de apoyo que tiene la CDC con laboratorios comerciales, y 3) Repositorios públicos (GISAID y NCBI). CONCLUSIONES: El objetivo del presente informe es describir la alta demanda de la realización de las pruebas diagnósticas para SARS-CoV-2 ante la nueva variante Ómicron (B.1.1.529) del SARS-CoV-2. La información provino de fuentes gubernamentales o de agencias internacionales que evaluaron e proceso de realización de las pruebas diagnósticas para SARS-CoV-2 ante la nueva variante Ómicron. Algunas agencias internacionales (OMS, OPS y CDC) recomiendan el incremento de las capacidades de realización de pruebas diagnósticas y secuenciación del genoma de especímenes sospechosos de ser variante Ómicron. También recomiendan el uso racional de pruebas diagnósticas. En el caso del CDC, se fortaleció el sistema de vigilancia a través de la obtención de especímenes provenientes de los laboratorios nacionales, laboratorios comerciales y repositorios públicos. La Comisión Europea recomienda incrementar las capacidades de las pruebas diagnósticas para la identificación rápida de la variante Ómicron. En el Reino Unido, frente a la alta prevalencia de COVID-19 se procedió a usar racionalmente las pruebas diagnósticas y las personas que tienen resultados positivos en las pruebas de antígenos pueden aislarse sin necesidad de realizar una prueba molecular confirmatoria. Ante la gran demanda de pruebas diagnósticas para COVID-19 y el récord de contagios en Argentina, la Administración Nacional de Medicamentos, Alimentos y Tecnología Médica (ANMAT), autorizó la realización de test de autoevaluación de venta exclusiva en farmacias para los productos aprobados de auto test de antígeno COVID-19 y test de prueba rápida para COVID-19, asimismo estas pruebas proporcionan resultados orientativos, sin valor diagnóstico concluyente. El Ministerio de Salud de Colombia, ante la sobredemanda de las pruebas diagnósticas moleculares y pruebas de antígenos para COVID-19, define criterios para el uso de estás en sus lineamientos y solamente se podrán utilizar la población de mayor riesgo, con comorbilidades o menores de tres años y las pruebas diagnósticas definidas por el Ministerio de Salud y Protección Social. En cuanto algunos países, como Ecuador, Colombia, Argentina a racionalizar las pruebas diagnósticas de COVID-19, priorizando a personas con comorbilidades, menores de 3 años de edad, o con prescripción médica. Concluyendo lo expuesto con los informes consultados, el linaje B.1.1.529 (Ómicron) del virus SARS-CoV-2 como variante de preocupación (VOC) para la salud pública es responsable de un aumento en la capacidad de transmisión, una mayor prevalencia de casos y una reducción d la capacidad de identificación de casos por escasez de pruebas diagnósticas; por consiguiente algunas agencias recomendaron incrementar la capacidad de los laboratorios en la realización de pruebas diagnósticas, así como el uso racional de éstas.

Population-level estimates of hepatitis C reinfection post scale-up of direct-acting antivirals among people who inject drugs.

BACKGROUND & AIMS: Scale-up of highly effective direct-acting antivirals (DAAs) for HCV among people who inject drugs (PWID) in Scotland has led to a reduction in the prevalence of viraemia in this population. However, the extent of reinfection among those treated with DAAs remains uncertain. We estimated HCV reinfection rates among PWID in Scotland by treatment setting, pre- and post-introduction of DAAs, and the potential number of undiagnosed reinfections resulting from incomplete follow-up testing. METHODS: Through linkage of national clinical and laboratory HCV data, a retrospective cohort of PWID who commenced treatment between 2000-2018 and achieved a sustained virological response (SVR) were followed up for reinfection to December 2019. Reinfection was defined as a positive HCV antigen or RNA test. RESULTS: Of 5,686 SVRs among 5,592 PWID, 4,126 (73%) had an HCV RNA or antigen test post-SVR. Of those retested, we identified 361 reinfections (3.9/100 person-years [PY]). The reinfection rate increased from 1.5/100 PY among PWID treated in 2000-2009 to 8.8/100 PY in 2017-2018. The highest reinfection rates were observed among those treated in prison (14.3/100 PY) and community settings (9.5/100 PY). Among those treated in the DAA era (2015-2018), 68% were tested within the first year post-SVR but only 30% in the second year; while 169 reinfections were diagnosed in follow-up, an estimated 200 reinfections (54% of the estimated total) had gone undetected. CONCLUSIONS: HCV reinfection rates among PWID in Scotland have risen alongside the scale-up of DAAs and broadened access to treatment for those at highest risk, through delivery in community drug services. Promotion of HCV testing post-SVR among PWID is essential to ensure those reinfected are identified and retreated promptly. LAY SUMMARY: Increased rates of hepatitis C reinfection in Scotland were observed following the rapid scale-up of highly effective direct-acting antiviral (DAA) treatments among people who inject drugs. This demonstrates that community-based treatment pathways are reaching high-risk groups, regarded vital in efforts to eliminate the virus. However, we estimate that less than half of reinfections have been detected in the DAA era because of inadequate levels of retesting beyond the first year following successful treatment. Sustained efforts that involve high coverage of harm reduction measures and high uptake of annual testing are required to ensure prompt diagnosis and treatment of those reinfected if the goals of elimination are to be met.

Reconciling Egg- and Antigen-Based Estimates of Schistosoma mansoni Clearance and Reinfection: A Modeling Study.

BACKGROUND: Despite decades of interventions, 240 million people have schistosomiasis. Infections cannot be directly observed, and egg-based Kato-Katz thick smears lack sensitivity, affected treatment efficacy and reinfection rate estimates. The point-of-care circulating cathodic antigen (referred to from here as POC-CCA+) test is advocated as an improvement on the Kato-Katz method, but improved estimates are limited by ambiguities in the interpretation of trace results. METHOD: We collected repeated Kato-Katz egg counts from 210 school-aged children and scored POC-CCA tests according to the manufacturer's guidelines (referred to from here as POC-CCA+) and the externally developed G score. We used hidden Markov models parameterized with Kato-Katz; Kato-Katz and POC-CCA+; and Kato-Katz and G-Scores, inferring latent clearance and reinfection probabilities at four timepoints over six-months through a more formal statistical reconciliation of these diagnostics than previously conducted. Our approach required minimal but robust assumptions regarding trace interpretations. RESULTS: Antigen-based models estimated higher infection prevalence across all timepoints compared with the Kato-Katz model, corresponding to lower clearance and higher reinfection estimates. Specifically, pre-treatment prevalence estimates were 85% (Kato-Katz; 95% CI: 79%-92%), 99% (POC-CCA+; 97%-100%) and 98% (G-Score; 95%-100%). Post-treatment, 93% (Kato-Katz; 88%-96%), 72% (POC-CCA+; 64%-79%) and 65% (G-Score; 57%-73%) of those infected were estimated to clear infection. Of those who cleared infection, 35% (Kato-Katz; 27%-42%), 51% (POC-CCA+; 41%-62%) and 44% (G-Score; 33%-55%) were estimated to have been reinfected by 9-weeks. CONCLUSIONS: Treatment impact was shorter-lived than Kato-Katz-based estimates alone suggested, with lower clearance and rapid reinfection. At 3 weeks after treatment, longer-term clearance dynamics are captured. At 9 weeks after treatment, reinfection was captured, but failed clearance could not be distinguished from rapid reinfection. Therefore, frequent sampling is required to understand these important epidemiological dynamics.

A case with SARS-CoV-2 reinfection from India.

A healthcare worker presented with fever, cough, headache and tested positive by SARS-CoV-2 real time reverse transcriptase polymerase chain reaction (qRT-PCR). He got admitted to hospital and recovered after 14 days. After 2 months, as a screening protocol considering the high risk setup he got tested and again found to be positive for SARS-CoV-2 by qRT-PCR. Our patient had detectable levels of Anti-SARS-CoV-2 IgG antibodies during the reinfection but found negative for Neutralizing antibodies (NAb). Our findings suggest that the person after the initial infection might not develop the desired protective immunity to prevent the reinfection as demonstrated by absence of NAb.

Occupational risk of SARS-CoV-2 infection and reinfection during the second pandemic surge: a cohort study.

OBJECTIVES: This cohort study including essential workers, assessed the risk and incidence of SARS-CoV-2 infection during the second surge of COVID-19 according to baseline serostatus and occupational sector. METHODS: Essential workers were selected from a seroprevalence survey cohort in Geneva, Switzerland and were linked to a state centralised registry compiling SARS-CoV-2 infections. Primary outcome was the incidence of virologically confirmed infections from serological assessment (between May and September 2020) to 25 January 2021, according to baseline antibody status and stratified by three predefined occupational groups (occupations requiring sustained physical proximity, involving brief regular contact or others). RESULTS: 10 457 essential workers were included (occupations requiring sustained physical proximity accounted for 3057 individuals, those involving regular brief contact, 3645 and 3755 workers were classified under 'Other essential occupations'). After a follow-up period of over 27 weeks, 5 (0.6%) seropositive and 830 (8.5%) seronegative individuals had a positive SARS-CoV-2 test, with an incidence rate of 0.2 (95% CI 0.1 to 0.6) and 3.2 (95% CI 2.9 to 3.4) cases per person-week, respectively. Incidences were similar across occupational groups. Seropositive essential workers had a 93% reduction in the hazard (HR of 0.07, 95% CI 0.03 to 0.17) of having a positive test during the follow-up with no significant between-occupational group difference. CONCLUSIONS: A 10-fold reduction in the hazard of being virologically tested positive was observed among anti-SARS-CoV-2 seropositive essential workers regardless of their sector of occupation, confirming the seroprotective effect of a previous SARS-CoV2 exposure at least 6 months after infection.

Recurrence of COVID-19 in a Patient With NMO Spectrum Disorder While Treating With Rituximab: A Case Report and Review of the Literature.

INTRODUCTION: In the context of coronavirus disease 2019 (COVID-19) pandemic, patients with neuromyelitis optica spectrum disorder (NMOSD) are vulnerable to develop COVID-19 due to the immunosuppressive therapy. The objective of this study is to describe a known case of NMOSD on rituximab who experienced 2 episodes of COVID-19. CASE REPORT: A 25-year-old woman, a known case of NMOSD on rituximab was diagnosed with asymptomatic COVID-19. Eight months later, following her last infusion of rituximab, she developed moderate COVID-19. After a partial recovery, she exhibited exacerbation of respiratory symptoms leading to readmission and invasive oxygenation. She was eventually discharged home after 31 days. Her monthly neurological evaluation did not reveal evidence of disease activity. She later received intravenous immunoglobulin and the decision was made to start rituximab again. CONCLUSIONS: Our case raises the possibility of persistent virus shedding and reactivation of severe acute respiratory syndrome coronavirus-2 in a patient with NMOSD and rituximab therapy. We aimed to emphasize a precise consideration of management of patients with NMOSD during the COVID-19 pandemic.