SARS-CoV-2 infection in asymptomatic healthcare workers at a clinic in Chile

Rapid Decline of SARS-CoV-2 Viral Load in Single vs. Double-Dose (Short-Interval <6 Weeks) ChAdOx nCoV-19 Vaccinated Health-Care Workers

The present work was carried out during the emergence of Delta Variant of Concern (VoC) and aimed to study the change in SARS CoV-2 viral load in Covishield vaccinated asymptomatic/mildly symptomatic health-care workers (HCWs) to find out the optimum isolation period. The SARS CoV-2 viral load was carried out in sequential samples of 55 eligible HCWs which included unvaccinated (UnV; n = 11), single-dose vaccinated (SDV, n = 20) and double-dose vaccinated [DDV, n = 24; short-interval (<6 weeks)] subjects. The mean load of envelope (E) gene on day 5 in SDV [0.42 × 105 copies/reaction] was significantly lower as compared to DDV [6.3 × 105 copies/reaction, P = 0.005] and UnV [6.6 × 105 copies/reaction, P = 0.001] groups. The rate of decline of SARS CoV-2 viral load in the initial 5 days of PCR positivity was significantly higher in SDV as compared to that in DDV (Mean log decline 0.39 vs. 0.19; P < 0.001). This was possibly due to interference of adenoviral immunity of first dose of adenovirus-vectored vaccine in double-dose vaccinated HCWs who had received vaccines within a shorter interval (<6 weeks).

Demographic Characteristics of Unvaccinated Asymptomatic and Symptomatic SARS-CoV-2 Cases in Barwon South West, Victoria, Australia

We investigated 328 SARS-CoV-2 cases in Barwon South West, Victoria, Australia, in the 2020 pre-vaccination period, comparing infections with symptoms to those that remained asymptomatic. De-identified self-reported data on case characteristics and symptom progression from three sequential questionnaires were examined. Multivariable logistic regression was used to model associations between demographic profiles and symptoms. Asymptomatic infections were more than three times as likely to be seen in ethnic minority groups than the Caucasian population after adjusting for gender and age [OR 3.2, 95% CI 1.5-6.7, p < 0.01] and were more common among cases of Asian background [OR 2.8, 95%CI 1.2-6.4]. Asymptomatic infections were also more common in youth and younger adults, but cases were approximately seven times more likely to be in seniors (≥65 years) compared with those 24 years of age or younger after adjusting for sex and ethnicity [OR 6.9, 95% CI 1.3-35.8]. The overrepresentation of ethnic minority groups among asymptomatic infections is suggestive of genetic haplotype variability by ethnic group, conferring greater cross-protection from other coronaviruses in the initial phase of the COVID-19 pandemic. Replication of this analysis in the post-vaccination era and reassessment of symptom expression according to ethnicity in a community with established vaccine and infection-induced immunity would determine whether this is a sustained association or one confined to the early stages of a pandemic in an immunologically naive population. These findings may, in part, reflect differences in testing patterns by ethnicity and true differences in disease expression, both of which are important to understand in order to inform transmission prevention strategies and tailored risk messaging according to ethnic background.

Molecular surveillance of potential SARS-CoV-2 reservoir hosts in wildlife rehabilitation centers

BACKGROUND

The COVID-19 pandemic, caused by SARS-CoV-2 infection, has become the most devastating zoonotic event in recent times, with negative impacts on both human and animal welfare as well as on the global economy. Although SARS-CoV-2 is considered a human virus, it likely emerged from animals, and it can infect both domestic and wild animals. This constitutes a risk for human and animal health including wildlife with evidence of SARS-CoV-2 horizontal transmission back and forth between humans and wild animals.

AIM

Molecular surveillance in different wildlife rehabilitation centers and wildlife associated institutions in Chile, which are critical points of animal-human interaction and wildlife conservation, especially since the aim of wildlife rehabilitation centers is to reintroduce animals to their original habitat.

MATERIALS AND METHODS

The survey was conducted in six WRCs and three wildlife associated institutions. A total of 185 samples were obtained from 83 individuals belonging to 15 different species, including vulnerable and endangered species. Each specimen was sampled with two different swabs: one oropharyngeal or nasopharyngeal according to the nostril diameter, and/or a second rectal sample. RNA was extracted from the samples and two different molecular assays were performed: first, a conventional RT-PCR with pan-coronavirus primers and a second SARS-CoV-2 qPCR targeting the N and S genes.

RESULTS

All 185 samples were negative for SARS-CoV-2.

CLINICAL RELEVANCE

This study constitutes the first report on the surveillance of SARS-CoV-2 from wildlife treated in rehabilitation centers in Chile, and supports the biosafety procedures adopted in those centers.

Whole-genome sequencing to investigate transmission of SARS-CoV-2 in the acute healthcare setting: a systematic review

BACKGROUND

Whole-genome sequencing (WGS) has been used widely to elucidate transmission of SARS-CoV-2 in acute healthcare settings, and to guide infection, prevention, and control (IPC) responses.

AIM

To systematically appraise available literature, published between January 1st, 2020 and June 30th, 2022, describing the implementation of WGS in acute healthcare settings to characterize nosocomial SARS-CoV-2 transmission.

METHODS

Searches of the PubMed, Embase, Ovid MEDLINE, EBSCO MEDLINE, and Cochrane Library databases identified studies in English reporting the use of WGS to investigate SARS-CoV-2 transmission in acute healthcare environments. Publications involved data collected up to December 31st, 2021, and findings were reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.

FINDINGS

In all, 3088 non-duplicate records were retrieved; 97 met inclusion criteria, involving 62 outbreak analyses and 35 genomic surveillance studies. No publications from low-income countries were identified. In 87/97 (90%), WGS supported hypotheses for nosocomial transmission, while in 46 out of 97 (47%) suspected transmission events were excluded. An IPC intervention was attributed to the use of WGS in 18 out of 97 (18%); however, only three (3%) studies reported turnaround times ≤7 days facilitating near real-time IPC action, and none reported an impact on the incidence of nosocomial COVID-19 attributable to WGS.

CONCLUSION

WGS can elucidate transmission of SARS-CoV-2 in acute healthcare settings to enhance epidemiological investigations. However, evidence was not identified to support sequencing as an intervention to reduce the incidence of SARS-CoV-2 in hospital or to alter the trajectory of active outbreaks.

Prevalence and factors associated with COVID-19 among healthcare workers at a university hospital in Thailand

Globally, healthcare workers (HCWs) have a high risk of SARS-CoV-2 infection, but less is known about healthcare workers in Thailand. We estimated the prevalence and risk factors for COVID-19 among HCWs in Bangkok, Thailand. A retrospective cohort study was conducted at a large tertiary care academic hospital in Thailand from May 2020 to May 2021. HCWs that presented with fever and/or acute respiratory tract symptoms who tested with RT-PCR were identified, and their clinical data were collected. There were 1432 HCWs with fever and/or acute respiratory tract symptoms during May 2020 and May 2021. A total of 167 patients were front-line HCWs and 1265 were non-front-line HCWs. Sixty HCWs (4.2%) developed COVID-19; 2 were front-line and 58 were non-front-line HCWs. The prevalence of COVID-19 in front-line HCWs was 1.7% (2/167), and 4.6% (58/1265) in non-front-line HCWs (P = .04). In addition, non-front-line HCWs, non-medical staffs, history of contact with a confirmed COVID-19 case at home/family, unvaccinated status, fair compliance to personal protective equipment (PPE) standard, and initial presentation with pneumonia were significantly more common in HCWs with COVID-19 than those without COVID-19 (P < .05). Front-line HCWs, history of contact with a confirmed COVID-19 case at the clinical care areas in the hospital, vaccinated status, good compliance to PPE standards, and initial presentation with upper respiratory infection were significantly more common in HCWs without COVID-19 than those with COVID-19 (P < .05). Multivariate analysis revealed history of exposure with confirmed COVID-19 case at home or in family, unvaccinated status, non-frontline-HCWs, non-medical staffs, and fair compliance to PPE standard to be independent factors associated with COVID-19 in HCWs. COVID-19 was more common in non-front-line HCWs at this tertiary hospital. Thai guidelines on infection prevention and control for COVID-19 seem to be effective in preventing SARS-CoV-2 transmission. Therefore, the adherence to these recommendations should be encouraged.

Phylogenetic and phylodynamic approaches to understanding and combating the early SARS-CoV-2 pandemic

Determining the transmissibility, prevalence and patterns of movement of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections is central to our understanding of the impact of the pandemic and to the design of effective control strategies. Phylogenies (evolutionary trees) have provided key insights into the international spread of SARS-CoV-2 and enabled investigation of individual outbreaks and transmission chains in specific settings. Phylodynamic approaches combine evolutionary, demographic and epidemiological concepts and have helped track virus genetic changes, identify emerging variants and inform public health strategy. Here, we review and synthesize studies that illustrate how phylogenetic and phylodynamic techniques were applied during the first year of the pandemic, and summarize their contributions to our understanding of SARS-CoV-2 transmission and control.

The role of routine SARS-CoV-2 screening of healthcare-workers in acute care hospitals in 2020: a systematic review and meta-analysis

Background

Healthcare workers (HCW) are at increased risk of infection with SARS-CoV-2. Vulnerable patient populations in particular must be protected, and clinics should not become transmission hotspots to avoid delaying medical treatments independent of COVID. Because asymptomatic transmission has been described, routine screening of asymptomatic HCW would potentially be able to interrupt chains of infection through early detection.

Methods

A systematic search was conducted in the Cochrane COVID-19 Study Register, Web of Science and WHO COVID‐19 Global literature on coronavirus with regard to non-incident related testing of healthcare workers using polymerase chain reaction on May 4th 2021. Studies since January 2020 were included. An assessment of risk of bias and representativeness was performed.

Results

The search identified 39 studies with heterogeneous designs. Data collection of the included studies took place from January to August 2020. The studies were conducted worldwide and the sample size of the included HCW ranged from 70 to 9449 participants. In total, 1000 of 51,700 (1.9%) asymptomatic HCW were tested positive for SARS-CoV-2 using PCR testing. The proportion of positive test results ranged between 0 and 14.3%. No study reported on HCW-screening related reductions in infected person-days.

Discussion and conclusions

The heterogeneous proportions might be explained by different regional incidences, lock-downs, and pre-analytical pitfalls that reduce the sensitivity of the nasopharyngeal swab. The very high prevalence in some studies indicates that screening HCW for SARS-CoV-2 may be important particularly in geographical regions and pandemic periods with a high-incidence. With low numbers and an increasing rate of vaccinated HCW, a strict cost–benefit consideration must be made, especially in times of low incidences. Since we found no studies that reported on HCW-screening related reductions in infected person-days, re-evaluation should be done when these are available.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07554-5.

Effectiveness of a digital data gathering system to manage the first pandemic wave among healthcare workers in a main European coronavirus disease 2019 (COVID-19) tertiary-care hospital

OBJECTIVE

To evaluate the information collected from workers infected with severe acute respiratory coronavirus virus 2 (SARS-CoV-2) or close contacts using a digital data gathering system (DDGS) developed at the onset of the coronavirus disease 2019 (COVID-19) pandemic to better manage the spread of infection at our hospital.

DESIGN

Observational retrospective study.

SETTING

Tertiary University Hospital "Spedali Civili" Hospital, Brescia, Italy.

PARTICIPANTS

Workers (most of whom are healthcare workers) employed at the hospital.

METHODS

The information collected by the DDGS was transferred to the IBM SPSS statistical software package and then statistically analyzed.

RESULTS

Overall, ∼16% of the hospital workforce was infected by SARS-CoV-2 in the first pandemic wave. Nurses were the professional category with the highest infection rate (∼15%). The asymptomatic rate of infection was between 31% and 62%. Positive molecular swabs were significantly more frequent in workers undergoing the test after sending a signaling form to our DDGS. Among workers sending the signaling forms, the information about symptoms was more predictive in terms of risk, compared to the close-contact information. The concordance between molecular swabs and subsequent serological testing was significantly higher in workers signaling their at-risk condition through the DDGS.

CONCLUSIONS

Overall, our data demonstrate the advantages of a digital system to gather information from workers, which is useful for managing emergencies such as the COVID-19 pandemic. This holds particularly true for large organizations such as hospitals.

Transmission of COVID-19 among healthcare workers - an epidemiological study during the first phase of the pandemic in Sweden

During the first phase of the COVID-19 pandemic in 2020, concerns were raised that healthcare workers (HCWs) were at high risk of infection. The aim of this study was to explore the transmission of COVID-19 among HCWs during a staff outbreak at an inpatient ward in Sweden 1 March to 31 May 2020. A mixed-methods approach was applied using several data sources. In total, 152 of 176 HCWs participated. The incidence of COVID-19 among HCWs was 33%. Among cases, 48 (96%) performed activities involving direct contact with COVID-19 patients. Contact tracing connected 78% of cases to interaction with another contagious co-worker. Only a few HCW cases reported contact with a confirmed COVID-19 case at home (n = 6; 12%) or in the community (n = 3; 6%). Multiple logistic regression identified direct care of COVID-19 patients and positive COVID-19 family contact as risk factors for infection (adjusted OR 8.4 and 9.0 respectively). Main interventions to stop the outbreak were physical distancing between HCWs, reinforcement of personal hygiene routines and rigorous surface cleaning. The personal protective equipment used in contact with patients was not changed in response to the outbreak. We highlight HCW-to-HCW transmission of COVID-19 in a hospital environment and the importance of preventing droplet and contact transmission between co-workers.

Severe acute respiratory coronavirus virus 2 (SARS-CoV-2) seroconversion and occupational exposure of employees at a Swiss university hospital: A large longitudinal cohort study

BACKGROUND

The dynamics of coronavirus disease 2019 (COVID-19) seroconversion of hospital employees are understudied. We measured the proportion of seroconverted employees and evaluated risk factors for seroconversion during the first pandemic wave.

METHODS

In this prospective cohort study, we recruited Geneva University Hospitals employees and sampled them 3 times, every 3 weeks from March 30 to June 12, 2020. We measured the proportion of seroconverted employees and determined prevalence ratios of risk factors for seroconversion using multivariate mixed-effects Poisson regression models.

RESULTS

Overall, 3,421 participants (29% of all employees) were included, with 92% follow-up. The proportion of seroconverted employees increased from 4.4% (95% confidence interval [CI], 3.7%-5.1%) at baseline to 8.5% [(95% CI, 7.6%-9.5%) at the last visit. The proportions of seroconverted employees working in COVID-19 geriatrics and rehabilitation (G&R) wards (32.3%) and non-COVID-19 G&R wards (12.3%) were higher compared to office workers (4.9%) at the last visit. Only nursing assistants had a significantly higher risk of seroconversion compared to office workers (11.7% vs 4.9%; P = .006). Significant risk factors for seroconversion included the use of public transportation (adjusted prevalence ratio, 1.59; 95% CI, 1.25-2.03), known community exposure to severe acute respiratory coronavirus virus 2 (2.80; 95% CI, 2.22-3.54), working in a ward with a nosocomial COVID outbreak (2.93; 95% CI, 2.27-3.79), and working in a COVID-19 G&R ward (3.47; 95% CI, 2.45-4.91) or a non-COVID-19 G&R ward (1.96; 95% CI, 1.46-2.63). We observed an association between reported use of respirators and lower risk of seroconversion (0.73; 95% CI, 0.55-0.96).

CONCLUSION

Additional preventive measures should be implemented to protect employees in G&R wards. Randomized trials on the protective effect of respirators are urgently needed.

Asymptomatic RT-PCR positive COVID-19 patients in orthopaedic pre-operative evaluation during the peak of the second wave

Introduction

Asymptomatic COVID-19 patients are the most challenging and feared obstacles in resuming these surgical procedures. The purpose of this study was to evaluate the proportion of asymptomatic carriers detected by RT-PCR in pre-operative orthopaedic evaluation during the peak of the second wave.

Methods

514 asymptomtomatic COVID-19 patients, negative for TOCC (Travel, Profession, Cluster, Contact) risk factors were observed retrospectively. A nasopharyFngeal RT-PCR test was obtained 48 to 72 h before the surgery in all cases. Possible risk factors for a positive test was identified.

Results

The detected asymptomatic COVID-19 infection rate during the peak of the second wave among the pre-operative orthopaedic patients was 12.3%. Younger age, female gender, longer duration of admission to RT-PCR test interval were found to be significant (p= < 0.05) risk factors for asymptomatic RT-PCR to be positive. The hazard ratio (HR) for being asymptomatic RT-PCR positive was 4.3 (p = 0. 025), while the RT-PCR was performed at 14 days, but the HR increased to 9.2 (p = 0.049) when the test was performed after 45 days.

Conclusion

According to our findings, pre-operative testing to rule out COVID-19 should be regarded as a critical step in preventing the disease clusters in hospitals.

Severe acute respiratory syndrome coronavirus 2 infection among healthcare workers in a tertiary public hospital in Curitiba, Brazil

BACKGROUND:

We aimed to describe the clinical characteristics of coronavirus disease 2019 (COVID-19) among healthcare workers (HCWs) in Curitiba, Brazil.

METHODS:

Upper respiratory samples from 1077 HCWs were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using reverse transcription polymerase chain reaction from June 16, 2020 to December 9, 2020.

RESULTS:

Overall, 32.7% of HCWs were infected. The positivity rates in symptomatic and asymptomatic HCWs were 39.2% and 15.9%, respectively. Hospital departments categorized as high-risk for exposure had the highest number of infected HCWs.

CONCLUSIONS:

Early diagnosis and isolation of infected HCWs remain key in controlling SARS-CoV-2 transmission because HCWs in close contact with COVID-19 patients are more likely to be infected than those who are not.

Global Percentage of Asymptomatic SARS-CoV-2 Infections Among the Tested Population and Individuals With Confirmed COVID-19 Diagnosis: A Systematic Review and Meta-analysis

IMPORTANCE

Asymptomatic infections are potential sources of transmission for COVID-19.

OBJECTIVE

To evaluate the percentage of asymptomatic infections among individuals undergoing testing (tested population) and those with confirmed COVID-19 (confirmed population).

DATA SOURCES

PubMed, EMBASE, and ScienceDirect were searched on February 4, 2021.

STUDY SELECTION

Cross-sectional studies, cohort studies, case series studies, and case series on transmission reporting the number of asymptomatic infections among the tested and confirmed COVID-19 populations that were published in Chinese or English were included.

DATA EXTRACTION AND SYNTHESIS

This meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Random-effects models were used to estimate the pooled percentage and its 95% CI. Three researchers performed the data extraction independently.

MAIN OUTCOMES AND MEASURES

The percentage of asymptomatic infections among the tested and confirmed populations.

RESULTS

Ninety-five unique eligible studies were included, covering 29 776 306 individuals undergoing testing. The pooled percentage of asymptomatic infections among the tested population was 0.25% (95% CI, 0.23%-0.27%), which was higher in nursing home residents or staff (4.52% [95% CI, 4.15%-4.89%]), air or cruise travelers (2.02% [95% CI, 1.66%-2.38%]), and pregnant women (2.34% [95% CI, 1.89%-2.78%]). The pooled percentage of asymptomatic infections among the confirmed population was 40.50% (95% CI, 33.50%-47.50%), which was higher in pregnant women (54.11% [95% CI, 39.16%-69.05%]), air or cruise travelers (52.91% [95% CI, 36.08%-69.73%]), and nursing home residents or staff (47.53% [95% CI, 36.36%-58.70%]).

CONCLUSIONS AND RELEVANCE

In this meta-analysis of the percentage of asymptomatic SARS-CoV-2 infections among populations tested for and with confirmed COVID-19, the pooled percentage of asymptomatic infections was 0.25% among the tested population and 40.50% among the confirmed population. The high percentage of asymptomatic infections highlights the potential transmission risk of asymptomatic infections in communities.

Asymptomatic SARS-CoV-2 infection: A systematic review and meta-analysis

Quantification of asymptomatic infections is fundamental for effective public health responses to the COVID-19 pandemic. Discrepancies regarding the extent of asymptomaticity have arisen from inconsistent terminology as well as conflation of index and secondary cases which biases toward lower asymptomaticity. We searched PubMed, Embase, Web of Science, and World Health Organization Global Research Database on COVID-19 between January 1, 2020 and April 2, 2021 to identify studies that reported silent infections at the time of testing, whether presymptomatic or asymptomatic. Index cases were removed to minimize representational bias that would result in overestimation of symptomaticity. By analyzing over 350 studies, we estimate that the percentage of infections that never developed clinical symptoms, and thus were truly asymptomatic, was 35.1% (95% CI: 30.7 to 39.9%). At the time of testing, 42.8% (95% prediction interval: 5.2 to 91.1%) of cases exhibited no symptoms, a group comprising both asymptomatic and presymptomatic infections. Asymptomaticity was significantly lower among the elderly, at 19.7% (95% CI: 12.7 to 29.4%) compared with children at 46.7% (95% CI: 32.0 to 62.0%). We also found that cases with comorbidities had significantly lower asymptomaticity compared to cases with no underlying medical conditions. Without proactive policies to detect asymptomatic infections, such as rapid contact tracing, prolonged efforts for pandemic control may be needed even in the presence of vaccination.

Investigation of intra-hospital SARS-CoV-2 transmission using nanopore whole-genome sequencing

BACKGROUND

During the SARS-CoV-2 pandemic, healthcare workers (HCWs) are being exposed to infection both at work and in their communities. Determining where HCWs might have been infected is challenging based on epidemiological data alone. At Akershus University Hospital, Norway, several clusters of possible intra-hospital SARS-CoV-2 transmission were identified based on routine contact tracing.

AIM

To determine whether clusters of suspected intra-hospital SARS-CoV-2 transmission could be resolved by combining whole genome sequencing (WGS) of SARS-CoV-2 with contact tracing data.

METHODS

Epidemiological data were collected during routine contact tracing of polymerase chain reaction-confirmed SARS-CoV-2-positive HCWs. Possible outbreaks were identified as wards with two or more infected HCWs defined as close contacts who tested positive for SARS-CoV-2 less than three weeks apart. Viral RNA from naso-/oropharyngeal samples underwent nanopore sequencing in direct compliance to the ARTIC Network protocol.

FINDINGS

Five outbreaks were suspected from contact tracing. Viral consensus sequences from 24 HCWs, two patients, and seven anonymous samples were analysed. Two outbreaks were confirmed, one refuted, and two remained undetermined. One new potential outbreak was discovered.

CONCLUSION

Combined with epidemiological data, nanopore WGS was a useful tool for investigating intra-hospital SARS-CoV-2 transmission. WGS helped to resolve questions about possible outbreaks and to guide local infection prevention and control measures.

Asymptomatic SARS-CoV-2 infection among healthcare workers in a non-COVID-19 teaching university hospital

Introduction: During the COVID-19 pandemic, most of the published reports on COVID-19 emphasized that health care workers (HCWs) get infected more than the general population representing one of the most vulnerable groups. However, that the real percentage of HCWs infected by SARS-CoV2 in Egypt remains unknown. The researchers conducted the current study to assess seroprevalence of SARS-CoV-2 IgG among HCWs working in a hospital with no SARS-CoV-2 patients, and to identify the potential factors associated with SARS-CoV2 IgG seropositivity.

Design and Methods: The current study is a cross-sectional study carried out among 455 HCWs at Cairo University Hospital. The researchers administered a questionnaire shortly before the SARS-CoV-2 rapid test is performed using closed-ended question format to obtain information on demographic data of the study participants including age, sex, specialty, clinical information including questions about medical conditions, and. history of previous exposure with a confirmed or suspected case of COVID-19, and history of COVID-19- compatible symptoms during the previous 14 days (cough, sore throat, runny nose, fatigue, shortness of breath, fever, headache, vomiting, diarrhea, anosmia, ageusia, and chills).

Results: We screened 455 HCWs for SARS-CoV-2 antibodies, 31.4% were in the high-risk group, and 68.6% in the low-risk group. The overall IgG seroprevalence was, 36 (7.9%) (95% CI 5.8 to 10.8). The IgG seroprevalence was significantly higher in low-risk group 11% (35/312) versus high-risk group 0.7% (1/143, p<0.001.

Conclusion: Low seropositivity rates for SARS-CoV-2 among HCWs is suggestive of lack of immunity and we are still far from herd immunity.