Varicella zoster virus outbreak in a long-term care unit of a tertiary care hospital in northern India.

Nosocomial outbreak of varicella zoster virus (VZV) has been reported when susceptible individuals encounter a case of chicken pox or shingles. A suspected VZV outbreak was investigated in a 50-bedded in-patient facility of Physical Medicine and Rehabilitation in a tertiary care multispecialty hospital. A 30-year-old female patient admitted with Pott's spine was clinically diagnosed with chicken pox on 31 December 2022. The following week, four more cases were identified in the same ward. All cases were diagnosed as laboratory-confirmed varicella zoster infection by PCR. Primary case was a housekeeping staff who was clinically diagnosed with chicken pox 3 weeks prior (9 December 2022). He returned to work on eighth day of infection (17 December 2022) after apparent clinical recovery but before the lesions had crusted over. Thirty-one HCWs were identified as contacts a and three had no evidence of immunity. Two of these susceptible HCWs had onset of chickenpox shortly after first dose of VZV vaccination was inoculated. All cases recovered after treatment with no reported complications. VZV infection is highly contagious in healthcare settings with susceptible populations. Prompt identification of cases and implementation of infection prevention and control measures like patient isolation and vaccination are essential for the containment of outbreaks.

Molecular epidemiology of a Parainfluenza Type 3 virus outbreak: Informing infection control measures on adult hematology wards.

OBJECTIVES: Parainfluenza virus type 3 (PIV3) outbreaks among hematology patients are associated with high morbidity and mortality. Prompt implementation of infection prevention (IP) measures has proven to be the most efficacious approach for controlling PIV3 outbreaks within this patient population. The most suitable IP measures can vary depending on the mode of virus transmission, which remains unidentified in most outbreaks. We describe the molecular epidemiology of an outbreak of PIV3 among hematology patients and the development of a new method that allows for the differentiation of outbreak and community strains, from which a closed outbreak could be inferred. METHODS: Patients were screened for respiratory viruses using multiplex-PCR. PIV3 positive samples with a cycle threshold (Ct)-value of <31 underwent a retrospective characterization via an in-house developed sequence analysis of the hemagglutinin-neuraminidase (HN) gene. RESULTS: Between July and September 2022, 31 hematology patients were identified with PIV3. Although infection control measures were implemented, the outbreak persisted for nine weeks. Sequencing the HN gene of 27 PIV3 strains from 27 patients revealed that all outbreak strains formed a distinct cluster separate from the control strains, suggestive of a nosocomial transmission route. CONCLUSIONS: Sequencing the HN gene of PIV3 strains in an outbreak setting enables outbreak strains to be distinguished from community strains. Early molecular characterization of PIV3 strains during an outbreak can serve as a tool in determining potential transmission routes. This, in turn, enables rapid implementation of targeted infection prevention measures, with the goal of minimizing the outbreak's duration and reducing associated morbidity and mortality.

Evidence from whole genome sequencing of aerosol transmission of SARS-CoV-2 almost 5 hours after hospital room turnover.

Experimental evidence suggests that Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) remains viable within aerosols with a half-life of approximately 3 hours; however, it remains unclear how long airborne SARS-CoV-2 can transmit infection. Whole genome sequencing during an outbreak suggested in-room transmission of SARS-CoV-2 to two patients admitted nearly 2 and 5 hours, respectively, after discharge of an asymptomatic infected patient. These findings suggest that airborne SARS-CoV-2 may transmit infection for over 4 hours, even in a hospital setting.

Incidence and transmission associated with respiratory viruses in an acute care facility: An observational study.

We estimated the extent of respiratory virus transmission over three pre-COVID-19 seasons. Of 16,273 assays, 22.9% (3,726) detected ≥1 respiratory virus. The frequency of putatively hospital-acquired infection ranged from 6.9% (influenza A/B) to 24.7% (adenovirus). The 176 clusters were most commonly associated with rhinovirus/enterovirus (70) and influenza A/B (62).

Integrated Genomic and Social Network Analyses of SARS-CoV-2 Transmission in the Healthcare Setting.

BACKGROUND: Infection prevention (IP) measures are designed to mitigate the transmission of pathogens in healthcare. Using large-scale viral genomic and social network analyses, we determined if IP measures used during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic were adequate in protecting healthcare workers (HCWs) and patients from acquiring SARS-CoV-2. METHODS: We performed retrospective cross-sectional analyses of viral genomics from all available SARS-CoV-2 viral samples collected at UC San Diego Health and social network analysis using the electronic medical record to derive temporospatial overlap of infections among related viromes and supplemented with contact tracing data. The outcome measure was any instance of healthcare transmission, defined as cases with closely related viral genomes and epidemiological connection within the healthcare setting during the infection window. Between November 2020 through January 2022, 12 933 viral genomes were obtained from 35 666 patients and HCWs. RESULTS: Among 5112 SARS-CoV-2 viral samples sequenced from the second and third waves of SARS-CoV-2 (pre-Omicron), 291 pairs were derived from persons with a plausible healthcare overlap. Of these, 34 pairs (12%) were phylogenetically linked: 19 attributable to household and 14 to healthcare transmission. During the Omicron wave, 2106 contact pairs among 7821 sequences resulted in 120 (6%) related pairs among 32 clusters, of which 10 were consistent with healthcare transmission. Transmission was more likely to occur in shared spaces in the older hospital compared with the newer hospital (2.54 vs 0.63 transmission events per 1000 admissions, P < .001). CONCLUSIONS: IP strategies were effective at identifying and preventing healthcare SARS-CoV-2 transmission.

Clinical evaluation of a multiplex droplet digital PCR for pathogen detection in critically ill COVID-19 patients with bloodstream infections.

BACKGROUND: Nosocomial bloodstream infections (nBSI) have emerged as a clinical concern for physicians treating COVID-19 patients. In this study, we aimed to evaluate the effectiveness of a multiplex ddPCR in detecting bacterial pathogens in the blood of COVID-19 critically ill patients. METHODS: This prospective diagnostic study included RT-PCR-confirmed COVID-19 patients admitted to our hospital from December 2022 to February 2023. A multiplex ddPCR assay was used to detect common bacterial pathogens and AMR genes in blood samples of the patients, along with antimicrobial susceptibility testing (AST). The diagnostic performance of the ddPCR assay was evaluated by comparing the results with those obtained through blood culture and clinical diagnosis. Additionally, the ability of ddPCR in detecting bacterial resistance was compared with the AST results. RESULTS: Of the 200 blood samples collected from 184 patients, 45 (22.5%) were positive using blood culture, while 113 (56.5%) were positive for bacterial targets using the ddPCR assay. The ddPCR assay outperformed blood culture in pathogen detection rate, mixed infection detection rate, and fungal detection rate. Acinetobacter baumannii and Klebsiella pneumoniae were the most commonly detected pathogens in COVID-19 critically ill patients, followed by Enterococcus and Streptococcus. Compared to blood culture, ddPCR achieved a sensitivity of 75.5%, specificity of 51.0%, PPV of 30.9%, and NPV of 87.8%, respectively. However, there were significant differences in sensitivity among different bacterial species, where Gram-negative bacteria have the highest sensitivity of 90.3%. When evaluated on the ground of clinical diagnosis, the sensitivity, specificity, PPV and NPV of ddPCR were 78.1%, 90.5%, 94.7%, and 65.5%, respectively. In addition, the ddPCR assay detected 23 cases of blaKPC, which shown a better consistent with clinical test results than other detected AMR genes. Compared to blaKPC, there were few other AMR genes detected, indicating that the application of other AMR gene detection in the COVID-19 critically ill patients was limited. CONCLUSION: The multiplex ddPCR assay had a significantly higher pathogen detection positivity than the blood culture, which could be an effective diagnostic tool for BSIs in COVID-19 patients and to improve patient outcomes and reduce the burden of sepsis on the healthcare system, though there is room for optimization of the panels used.- Adjusting the targets to include E. faecalis and E. faecium as well as Candida albicans and Candida glabrata could improve the ddPCR' s effectiveness. However, further research is needed to explore the potential of ddPCR in predicting bacterial resistance through AMR gene detection.

Genotypic shift in rotavirus associated with neonatal outbreaks in Seoul, Korea.

BACKGROUND: Rotavirus group A (RVA) is a causative agent of acute gastroenteritis among young children worldwide, despite the global expansion of rotavirus vaccination. In Korea, although the prevalence of RVA has been reduced among young children owing to vaccination, nosocomial infections still occur among neonates. OBJECTIVES: The aim of this study was to investigate the molecular epidemiology of RVA strains associated with several neonatal outbreaks in Seoul from 2017 to 2020. STUDY DESIGN: Clinical and environmental samples were collected and screened for the presence of RVA using ELISA and PCR targeting VP6, respectively. RVA-positive strains were genotyped via RT-PCR and subsequent sequencing of VP4 and VP7 and were phylogenetically compared with RVA strains from other countries. RESULTS: During 2017-2020, a total of 15 RVA outbreaks occurred at neonatal facilities (six in hospital neonatal wards and nine in postpartum care centers) in Seoul, and only two RVA genotypes were detected: G4P[6] and G8P[6]. G8P[6] emerged in Seoul November 2018 and immediately became the predominant genotype among neonates, at least up to 2020. Phylogenetic analysis revealed that the G8P[6] genotype in this study was closely related to G8P[6] strains first identified in Korea in 2017, but differed from G8P[6] strains detected in Africa. CONCLUSIONS: A novel G8P[6] genotype of RVA strains has emerged and caused outbreaks among neonates in Seoul. Continued surveillance for circulating RVA genotypes is imperative to monitor genotype changes and their potential risks to public health.

Role of hospital environmental surfaces in the transmission of the severe acute respiratory syndrome - Coronavirus-2.

INTRODUCTION: Severe acute respiratory syndrome - Coronavirus-2 (SARS-CoV-2) is mainly transmitted via respiratory secretions through coughing, sneezing, or contact with contaminated surfaces. This virus can be present in feces and many body fluids. The study aimed to screen the hospital environment as a potential source for SARS-CoV-2 transmission and identify the hospital zones with the highest contamination levels. METHODOLOGY: Swabs were collected from different sites in the hospital before and after routine cleaning/disinfection, transported in vials containing 1-3 mL of viral transport medium, and stored at -80 ℃ as soon as possible until the time of testing. The real-time reverse-transcription PCR (rRT-PCR) system targeting RNA-dependent RNA polymerase and E genes was used to detect the SARS-CoV-2 RNA. RESULTS: Moderate environmental contamination by SARS-CoV-2 RNA was detected by rRT-PCR before routine cleaning/disinfection (52% of the swabs were positive). The hospital surfaces with the highest contamination levels were elevators' buttons, sinks and faucets' handles at the waiting rooms, patient's room and bathroom, call buttons and telephones in the patient's room, toilet bowl surface, the doorknob and light switches at the X-ray room, and the computer keyboard at the staffroom. All the swabs collected after routine cleaning/disinfection were negative for SARS-CoV-2 RNA by rRT-PCR. CONCLUSIONS: The hospital environment is a high-risk area that can be contaminated by SARS-CoV-2 through contact, respiratory, and maybe fecal shedding of the virus. To limit this fatal virus transmission, strict adherence to proper hand hygiene with frequent optimal decontamination of hospital environmental surfaces is essential.

Chapare Hemorrhagic Fever and Virus Detection in Rodents in Bolivia in 2019.

BACKGROUND: In June 2019, the Bolivian Ministry of Health reported a cluster of cases of hemorrhagic fever that started in the municipality of Caranavi and expanded to La Paz. The cause of these cases was unknown. METHODS: We obtained samples for next-generation sequencing and virus isolation. Human and rodent specimens were tested by means of virus-specific real-time quantitative reverse-transcriptase-polymerase-chain-reaction assays, next-generation sequencing, and virus isolation. RESULTS: Nine cases of hemorrhagic fever were identified; four of the patients with this illness died. The etiologic agent was identified as Mammarenavirus Chapare mammarenavirus, or Chapare virus (CHAPV), which causes Chapare hemorrhagic fever (CHHF). Probable nosocomial transmission among health care workers was identified. Some patients with CHHF had neurologic manifestations, and those who survived had a prolonged recovery period. CHAPV RNA was detected in a variety of human body fluids (including blood; urine; nasopharyngeal, oropharyngeal, and bronchoalveolar-lavage fluid; conjunctiva; and semen) and in specimens obtained from captured small-eared pygmy rice rats (Oligoryzomys microtis). In survivors of CHHF, viral RNA was detected up to 170 days after symptom onset; CHAPV was isolated from a semen sample obtained 86 days after symptom onset. CONCLUSIONS: M. Chapare mammarenavirus was identified as the etiologic agent of CHHF. Both spillover from a zoonotic reservoir and possible person-to-person transmission were identified. This virus was detected in a rodent species, O. microtis. (Funded by the Bolivian Ministry of Health and others.).

Repeated transmission of SARS-CoV-2 in an overcrowded Irish emergency department elucidated by whole-genome sequencing.

AIM: To provide a detailed genomic-epidemiological description of a complex multi-ward SARS-CoV-2 outbreak, which originated in the crowded emergency department (ED) in our hospital during the third wave of the COVID-19 pandemic, and was elucidated promptly by local whole-genome sequencing (WGS). METHODS: SARS-CoV-2 was detected by reverse transcriptase real-time polymerase chain reaction on viral RNA extracted from nasopharyngeal swabs. WGS was performed using an Oxford MinION Mk1C instrument following the ARTIC v3 sequencing protocol. High-quality consensus genomes were assembled with the artic-ncov2019 bioinformatics pipeline and viral phylogenetic trees were built, inferred by maximum-likelihood. Clusters were defined using a threshold of 0-1 single nucleotide polymorphisms (SNPs) between epidemiologically linked sequences. RESULTS: In April 2021, outbreaks of COVID-19 were declared on two wards at University Hospital Limerick after 4 healthcare-associated SARS-CoV-2 infections were detected by post-admission surveillance testing. Contact tracing identified 12 further connected cases; all with direct or indirect links to the ED 'COVID Zone'. All sequences were assigned to the Pangolin B.1.1.7 lineage by WGS, and SNP-level analysis revealed two distinct but simultaneous clusters of infections. Repeated transmission in the ED was demonstrated, involving patients accommodated on trolleys in crowded areas, resulting in multiple generations of infections across three inpatient hospital wards and subsequently to the local community. These findings informed mitigation efforts to prevent cross-transmission in the ED. CONCLUSION: Cross-transmission of SARS-CoV-2 occurred repeatedly in an overcrowded emergency department. Viral WGS elucidated complex viral transmission networks in our hospital and informed infection, prevention and control practice.

Prevalence and Clinical Impact of Coinfection in Patients with Coronavirus Disease 2019 in Korea.

Coinfection rates with other pathogens in coronavirus disease 2019 (COVID-19) varied during the pandemic. We assessed the latest prevalence of coinfection with viruses, bacteria, and fungi in COVID-19 patients for more than one year and its impact on mortality. A total of 436 samples were collected between August 2020 and October 2021. Multiplex real-time PCR, culture, and antimicrobial susceptibility testing were performed to detect pathogens. The coinfection rate of respiratory viruses in COVID-19 patients was 1.4%. Meanwhile, the rates of bacteria and fungi were 52.6% and 10.5% in hospitalized COVID-19 patients, respectively. Respiratory syncytial virus, rhinovirus, Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were the most commonly detected pathogens. Ninety percent of isolated A. baumannii was non-susceptible to carbapenem. Based on a multivariate analysis, coinfection (odds ratio [OR] = 6.095), older age (OR = 1.089), and elevated lactate dehydrogenase (OR = 1.006) were risk factors for mortality as a critical outcome. In particular, coinfection with bacteria (OR = 11.250), resistant pathogens (OR = 11.667), and infection with multiple pathogens (OR = 10.667) were significantly related to death. Screening and monitoring of coinfection in COVID-19 patients, especially for hospitalized patients during the pandemic, are beneficial for better management and survival.

Linked nosocomial COVID-19 outbreak in three facilities for people with intellectual and developmental disabilities due to SARS-CoV-2 variant B.1.1.519 with spike mutation T478K in the Netherlands.

BACKGROUND: Individuals with intellectual and developmental disabilities (IDD) living in congregated settings have increased risk of COVID-19 infection and mortality. Little is known about variant B.1.1.519 with spike mutation T478K, dominant in Mexico. We describe a linked SARS-CoV-2 B.1.1.519 outbreak in three IDD facilities in the Netherlands. METHODS: Following notification of the index, subsequent cases were identified through serial PCR group testing. Positive specimens were submitted for whole-genome-sequencing. Clinical information was gathered through interviews with staff members of the three facilities. RESULTS: Attack rate (AR) in clients of the index facility was 92% (23/25), total AR in clients 45% (33/73) and in staff members 24% (8/34). 55% (18/33) of client cases were asymptomatic, versus 25% (2/8) of staff members. Five client cases (15%) were hospitalized, two died (6%). Sequencing yielded the same specific B.1.1.519 genotype in all three facilities. No significant difference in median viral load was established comparing the B.1.1.519 variant with other circulating variants. The index of the linked outbreak reported no travel history or link to suspected or confirmed cases suggesting regional surveillance. Observed peak regional prevalence of B.1.1.519 during the outbreak supports this. CONCLUSION: AR, morbidity and mortality prior to control measures taking effect were high, probably related to the specific characteristics of the IDD setting and its clients. We assessed no evidence for intrinsic contributing properties of variant B.1.1.519. Our study argues for enhanced infection prevention protocols in the IDD setting, and prioritization of this group for vaccination against COVID-19.

Nosocomial Transmission of SARS-CoV-2 Involving Vaccinated Health Care Workers.

COVID-19 vaccination has proven to be effective at preventing symptomatic disease but there are scarce data to fully understand whether vaccinated individuals can still behave as SARS-CoV-2 transmission vectors. Based on viral genome sequencing and detailed epidemiological interviews, we report a nosocomial transmission event involving two vaccinated health care-workers (HCWs) and four patients, one of them with fatal outcome. Strict transmission control measures, as during the prevaccination period, must be kept between HCWs and HCWs-patients in nosocomial settings. IMPORTANCE COVID-19 vaccination has proven to be effective at preventing symptomatic disease. Although some transmission events involving vaccinated cases have also been reported, scarce information is still available to fully understand whether vaccinated individuals may still behave as vectors in SARS-CoV-2 transmission events. Here, we report a SARS-CoV-2 nosocomial transmission event, supported on whole genome sequencing, in early March 2021 involving two vaccinated HCWs and four patients in our institution. Strict transmission control measures between HCWs and HCWs - patients in nosocomial settings must not be relaxed, and should be kept as strictly as during the prevaccination period.

Managing Emergent Surgery for Ruptured Abdominal Aortic Aneurysm during the COVID-19 Pandemic.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has become a global pandemic which may compromise the management of vascular emergencies. An uncompromised treatment for ruptured abdominal aortic aneurysm (rAAA) during such a health crisis represents a challenge. This study aimed to demonstrate the treatment outcomes of rAAA and the perioperative prevention of cross-infection under the COVID-19 pandemic. METHODS: In cases of rAAA during the pandemic, a perioperative workflow was applied to expedite coronavirus testing and avoid pre-operative delay, combined with a strategy for preventing cross-infection. Data of rAAA treated in 11 vascular centers between January-March 2020 collected retrospectively were compared to the corresponding period in 2018 and 2019. RESULTS: Eight, 12, and 14 rAAA patients were treated in 11 centers in January-March 2018, 2019, and 2020, respectively. An increased portion were treated at local hospitals with a comparable outcome compared with large centers in Guangzhou. With EVAR-first strategy, 85.7% patients with rAAA in 2020 underwent endovascular repair, similar to that in 2018 and 2019. The surgical outcomes during the pandemic were not inferior to that in 2018 and 2019. The average length of ICU stay was 1.8 ± 3.4 days in 2020, tending to be shorter than that in 2018 and 2019, whereas the length of hospital stay was similar among 3 years. The in-hospital mortality of 2018, 2019, and 2020 was 37.5%, 25.0%, and 14.3%, respectively. Three patients undergoing emergent surgeries were suspected of COVID-19, though turned out to be negative after surgery. CONCLUSIONS: Our experience for emergency management of rAAA and infection prevention for healthcare providers is effective in optimizing emergent surgical outcomes during the COVID-19 pandemic.

Patient health records and whole viral genomes from an early SARS-CoV-2 outbreak in a Quebec hospital reveal features associated with favorable outcomes.

The first confirmed case of COVID-19 in Quebec, Canada, occurred at Verdun Hospital on February 25, 2020. A month later, a localized outbreak was observed at this hospital. We performed tiled amplicon whole genome nanopore sequencing on nasopharyngeal swabs from all SARS-CoV-2 positive samples from 31 March to 17 April 2020 in 2 local hospitals to assess viral diversity (unknown at the time in Quebec) and potential associations with clinical outcomes. We report 264 viral genomes from 242 individuals-both staff and patients-with associated clinical features and outcomes, as well as longitudinal samples and technical replicates. Viral lineage assessment identified multiple subclades in both hospitals, with a predominant subclade in the Verdun outbreak, indicative of hospital-acquired transmission. Dimensionality reduction identified two subclades with mutations of clinical interest, namely in the Spike protein, that evaded supervised lineage assignment methods-including Pangolin and NextClade supervised lineage assignment tools. We also report that certain symptoms (headache, myalgia and sore throat) are significantly associated with favorable patient outcomes. Our findings demonstrate the strength of unsupervised, data-driven analyses whilst suggesting that caution should be used when employing supervised genomic workflows, particularly during the early stages of a pandemic.

Health Care-Acquired Viral Respiratory Diseases.

Health care-acquired viral respiratory infections are common and cause increased patient morbidity and mortality. Although the threat of viral respiratory infection has been underscored by the coronavirus disease 2019 (COVID-19) pandemic, respiratory viruses have a significant impact in health care settings even under normal circumstances. Studies report decreased nosocomial transmission when aggressive infection control measures are implemented, with more success noted when using a multicomponent approach. Influenza vaccination of health care personnel furthers decrease rates of transmission; thus, mandatory vaccination is becoming more common. This article discusses the epidemiology, transmission, and control of health care-associated respiratory viral infections.

Current Insights Into Respiratory Virus Transmission and Potential Implications for Infection Control Programs : A Narrative Review.

Policies to prevent respiratory virus transmission in health care settings have traditionally divided organisms into Droplet versus Airborne categories. Droplet organisms (for example, influenza) are said to be transmitted via large respiratory secretions that rapidly fall to the ground within 1 to 2 meters and are adequately blocked by surgical masks. Airborne pathogens (for example, measles), by contrast, are transmitted by aerosols that are small enough and light enough to carry beyond 2 meters and to penetrate the gaps between masks and faces; health care workers are advised to wear N95 respirators and to place these patients in negative-pressure rooms. Respirators and negative-pressure rooms are also recommended when caring for patients with influenza or SARS-CoV-2 who are undergoing "aerosol-generating procedures," such as intubation. An increasing body of evidence, however, questions this framework. People routinely emit respiratory particles in a range of sizes, but most are aerosols, and most procedures do not generate meaningfully more aerosols than ordinary breathing, and far fewer than coughing, exercise, or labored breathing. Most transmission nonetheless occurs at close range because virus-laden aerosols are most concentrated at the source; they then diffuse and dilute with distance, making long-distance transmission rare in well-ventilated spaces. The primary risk factors for nosocomial transmission are community incidence rates, viral load, symptoms, proximity, duration of exposure, and poor ventilation. Failure to appreciate these factors may lead to underappreciation of some risks (for example, overestimation of the protection provided by medical masks, insufficient attention to ventilation) or misallocation of limited resources (for example, reserving N95 respirators and negative-pressure rooms only for aerosol-generating procedures or requiring negative-pressure rooms for all patients with SARS-CoV-2 infection regardless of stage of illness). Enhanced understanding of the factors governing respiratory pathogen transmission may inform the development of more effective policies to prevent nosocomial transmission of respiratory pathogens.

Comprehensive infection control measures prevent hospital-acquired severe acute respiratory syndrome coronavirus 2 infection: A single-center prospective cohort study and seroprevalence survey.

BACKGROUND: Coronavirus disease (COVID-19) is associated with a high mortality rate in older adults; therefore, it is important for medical institutions to take measures to prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission. This study aimed to assess the risk of SARS-CoV-2 infection among healthcare workers (HCWs) and the effectiveness of infection control measures. METHODS: This study had a cross-sectional component and a prospective cohort component. The cross-sectional component comprised an anti-SARS-CoV-2 antibody survey among HCWs at a medical center in Saitama City, Japan. In the prospective cohort component, HCWs at the same medical center were tested for anti-SARS-CoV-2 antibodies monthly over a 3-month period (May to July 2020) to assess the effectiveness of infection prevention measures, including personal protective equipment use. All participants in the cohort study also participated in the antibody survey. The primary outcome was anti-SARS-CoV-2 antibody (measured using Elecsys® Anti-SARS-CoV-2) positivity based on whether participants were engaged in COVID-19-related medical care. Other risk factors considered included occupational category, age, and sex. RESULTS: In total, 607 HCWs participated in the antibody survey and 116 doctors and nurses participated in the cohort study. Only one of the 607 participants in the survey tested positive for anti-SARS-CoV-2 antibodies. All participants in the cohort study were anti-SARS-CoV-2 antibody negative at baseline and remained antibody negative. Engaging in the care of COVID-19 patients did not increase the risk of antibody positivity. During the study period, a total of 30 COVID-19 in-patients were treated in the hospital. CONCLUSIONS: The infection control measures in the hospital protected HCWs from nosocomially acquired SARS-CoV-2 infection; thus, HCWs should engage in COVID-19-related medical care with confidence provided that they adhere to infectious disease precautions.