Nosocomial COVID-19: experience from a large acute NHS Trust in South-West London

Taylor, Jennifer; Rangaiah, Jayakeerthi; Narasimhan, Sridhar; Clark, John L.; Alexander, Z; Manuel, Rohini; Balasegaram, Sooria

doi:10.1016/j.jhin.2020.08.018

Cited by 40 publications

(51 citation statements)

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“…8 Applying a similar case definition, Taylor et al found probable nosocomial cases represented 11.3% of confirmed cases within a major London trust admitted between 6 th March to 12 April 2020; mortality was unreported in this study. 7 These reports preceded recognition of high-profile nosocomial outbreaks across several UK hospitals. 15,16 Thus, reliable estimates of the true impact of hospital-acquired covid-19 infection remain hampered by a paucity of publicly-available data at national and regional levels.…”

Section: Introductionmentioning

confidence: 99%

The burden of nosocomial covid-19: results from the Wales multi-centre retrospective observational study of 2518 hospitalised adults

Ponsford

Jefferies

Davies³

et al. 2021

Preprint

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ObjectivesTo define the burden of nosocomial (hospital-acquired) novel pandemic coronavirus (covid-19) infection among adults hospitalised across Wales.DesignRetrospective observational study of adult patients with polymerase chain reaction (PCR)-confirmed SARS-CoV-2 infection between 1st March – 1st July 2020 with a recorded hospital admission within the subsequent 31 days. Outcomes were collected up to 20th November using a standardised online data collection tool.SettingService evaluation performed across 18 secondary or tertiary care hospitals.Participants4112 admissions with a positive SARS-CoV-2 PCR result between 1st March to 1st July 2020 were screened. Anonymised data from 2518 participants were returned, representing over 60% of adults hospitalised across the nation of Wales.Main outcome measuresThe prevalence and outcomes (death, discharge) for nosocomial covid-19, assessed across of a range of possible case definitions.ResultsInpatient mortality rates for nosocomial covid-19 ranged from 38% to 42% and remained consistently higher than participants with community-acquired infection (31% to 35%) across a range of case definitions. Participants with nosocomial-acquired infection were an older, frailer, and multi-morbid population than those with community-acquired infection. Based on the Public Health Wales case definition, 50% of participants had been admitted for 30 days prior to diagnostic testing.ConclusionsThis represents the largest assessment of clinical outcomes for patients with nosocomial covid-19 in the UK to date. These findings suggest that inpatient mortality rates from nosocomial-infection are likely higher than previously reported, emphasizing the importance of infection control measures, and supports prioritisation of vaccination for covid-19 negative admissions and trials of post-exposure prophylaxis in inpatient cohorts.Trial registrationThis project was approved and sponsored by the Welsh Government, as part of a national audit and quality improvement scheme for patients hospitalised covid-19 across Wales.Key MessagesWhat is already known on this topicWe searched PubMed and ISI Web of Science up until 31-December-2020 for studies reporting on patient outcomes following hospital-acquired infection due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We identified a range of case-definitions for hospital-acquired infection, based on timing of diagnostic testing 5 to 15 days following admission. The largest and only multi-centre study concluded individuals with nosocomial infection are at a lower risk of death from SARS-CoV-2 than those infected in the community, however, was performed early in the pandemic and utilised a conservative definition of nosocomial infection.What this study addsOur multi-centre observational study represents the largest assessment of clinical outcomes for patients with nosocomial covid-19 in the UK to date, and suggests the burden of nosocomial SARS-CoV-2 infection has been underestimated. Nosocomial-infection occurred in older, frailer, and multi-morbid individuals, and was consistently associated with greater inpatient mortality than amongst those who were infected in the community across a spectrum of case-definitions. Our findings support implementation of enhanced infection control measures to reduce this burden during future waves, especially given the recent emergence of novel viral variants with enhanced transmissibility. Furthermore, roughly half of the patients meeting the Public Health Wales definition of definite nosocomial SARS-CoV-2 infection had been admitted for 30 days prior to diagnosis, highlighting a potential window of opportunity for inpatient pre-exposure and/or post-exposure prophylaxis.

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Section: Introductionmentioning

confidence: 99%

The burden of nosocomial covid-19: results from the Wales multi-centre retrospective observational study of 2518 hospitalised adults

Ponsford

Jefferies

Davies³

et al. 2021

Preprint

View full text Add to dashboard Cite

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“…Alternatively, healthcare workers (HCWs) may be routinely tested to prevent nosocomial transmission to patients who may have other comorbidities 2,3 . Both of these populations have a substantially higher risk of fatality from COVID-19 infection than the general population 4,5 . In the UK, testing commonly uses polymerase chain reaction (PCR) to detect the presence of viral RNA in the nasopharynx of those sampled 6 .…”

Section: Introductionmentioning

confidence: 99%

Estimating the effectiveness of routine asymptomatic PCR testing at different frequencies for the detection of SARS-CoV-2 infections

Hellewell

Russell

Beale

et al. 2020

Preprint

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BackgroundRoutine asymptomatic testing using RT-PCR of people who interact with vulnerable populations, such as medical staff in hospitals or care workers in care homes, has been employed to help prevent outbreaks among vulnerable populations. Although the peak sensitivity of RT-PCR can be high, the probability of detecting an infection will vary throughout the course of an infection. The effectiveness of routine asymptomatic testing will therefore depend on how testing and PCR detection varies over time.MethodsWe fitted a Bayesian statistical model to a dataset of twice weekly PCR tests of UK healthcare workers performed by self-administered nasopharyngeal swab, regardless of symptoms. We jointly estimated times of infection and the probability of a positive PCR test over time following infection, then compared asymptomatic testing strategies by calculating the probability that a symptomatic infection is detected before symptom onset and the probability that an asymptomatic infection is detected within 7 days of infection.FindingsWe estimated that the probability that the PCR test detected infection peaked at 77% (54 - 88%) 4 days after infection, decreasing to 50% (38 - 65%) by 10 days after infection. Our results suggest a substantially higher probability of detecting infections 1–3 days after infection than previously published estimates. We estimated that testing every other day would detect 57% (33-76%) of symptomatic cases prior to onset and 94% (75-99%) of asymptomatic cases within 7 days if test results were returned within a day.InterpretationOur results suggest that routine asymptomatic testing can enable detection of a high proportion of infected individuals early in their infection, provided that the testing is frequent and the time from testing to notification of results is sufficiently fast.FundingWellcome Trust, National Institute for Health Research (NIHR) Health Protection Research Unit, Medical Research Council (UKRI)Research in contextEvidence before this studyA number of studies have investigated the relationship between viral load of SARS-CoV-2 and the presence and severity of symptoms of COVID-19. Furthermore, a handful of studies have looked in detail at how the probability of detection by PCR varies over the course of an entire infection. We searched PubMed, BioRxiv, and MedRxiv for English-language articles with the search terms (“covid-19” OR “coronavirus” OR “SARS-CoV-2”) AND (“test” OR “detection” OR “PCR” OR “polymerase chain reaction” OR “RT-PCR” OR “reverse transcriptase” OR “swab” OR “antigen” OR “symptoms” OR “RNA”) AND (“regular” OR “widespread” OR “shedding” OR “health-care workers” OR “HCW” OR “regular”) AND (“asymptomatic” OR “pre-symptomatic” OR “exposure”). This search returned a total of 396 results, of which 21 were studies that either gathered similar data, i.e. symptom, antibody and PCR test data longitudinally, or they specifically investigated PCR sensitivity over the course of infection. Only one study directly attempted to fit a similar PCR positivity curve, but no study inferred unobserved infection times for individuals and used those estimates to jointly fit (across all individuals) the probability of a positive PCR test as a function of time since infection.Added value of this studyOur study extends the existing literature in two specific ways. First we infer infection times for all individuals using a rigorous Bayesian framework and within our model we directly use the inferred posterior distributions of infection time to fit a curve across all individuals to characterise the probability of detection via PCR test over the course of infection. Because HCWs in our dataset were tested regardless of symptoms, many of these tests were performed close to the time of infection and therefore help to characterise our probability of detection estimates, in contrast to earlier datasets that only include tests performed as a result of symptom onset or hospitalisation. Second, we incorporated these estimates into a model of testing frequency to provide insights into the likely effectiveness of routine testing in settings like hospitals.Implications of all the available evidenceRoutine asymptomatic testing by PCR is being used in many settings with the aim of preventing outbreaks within vulnerable populations. We present evidence that the majority of SARS-CoV-2 infections can be detected prior to symptom onset (or within 7 days if there is no symptom onset) by a routine asymptomatic testing regime with a high enough testing frequency and short delay between testing and notification of cases. Therefore, routine asymptomatic testing regimes can be calibrated using our findings to help optimise infection detection.

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“…Most COVID-19 transmission studies to date have utilised epidemiological analysis alone to identify outbreaks, including those from the UK (6) (7), China (8), France (9) and South Korea (10). The main limitation with using epidemiology alone is that when point prevalence is high, for instance at 2.2% in London during the first wave in April 2020 (11), this increases the chance two people in epidemiological contact are independent cases.…”

Section: Introductionmentioning

confidence: 99%

“…Nosocomial infection is reported to account for around 10-20% of all confirmed cases (18) (19) (6) (20) often in designated outbreaks (6) (7) (8) (9) (10) and with a crude death rate of up to 30% (19). The most likely routes of transmission are between patients and involving healthcare workers (HCW), with potential for all combinations of directionality to occur within the same nosocomial cluster.…”

Section: Introductionmentioning

confidence: 99%

Combined epidemiological and genomic analysis of nosocomial SARS-CoV-2 transmission identifies community social distancing as the dominant intervention reducing outbreaks

Snell

Fisher

Taj

et al. 2020

Preprint

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Many healthcare facilities report SARS-CoV-2 outbreaks but transmission analysis is complicated by the high prevalence of infection and limited viral genetic diversity. The contribution of different vectors to nosocomial infection or the effectiveness of interventions is therefore currently unclear. Detailed epidemiological and viral nanopore sequence data were analysed from 574 consecutive patients with a PCR positive SARS-CoV-2 test between March 13th and March 31st, when the pandemic first impacted on a large, multisite healthcare institution in London. During this time the first major preventative interventions were introduced, including progressive community social distancing (CSD) policies leading to mandatory national lockdown, exclusion of hospital visitors, and introduction of universal surgical facemask-use by healthcare-workers (HCW). Incidence of nosocomial cases, community SARS-CoV-2 cases and infection in a cohort of 228 HCWs followed the same dynamic course, decreasing shortly after introduction of CSD measures and prior to the main hospital-based interventions. We investigated clusters involving nosocomial cases based on overlapping ward-stays during the 14-day incubation period and SARS-CoV-2 genome sequence similarity. Our method placed 63 (79%) of 80 sequenced probable and definite nosocomial cases into 14 clusters containing a median of 4 patients (min 2, max 19) No genetic support was found for the majority of epidemiological clusters (31/44, 70%) and genomics revealed multiple contemporaneous outbreaks within single epidemiological clusters. We included a measure of hospital enrichment compared to community cases to increase confidence in our clusters, which were 1-14 fold enriched. Applying genomics, we could provide a robust estimate of the incubation period for nosocomial transmission, with a median lower bound and upper bound of 6 and 9 days respectively. Six (43%) clusters spanned multiple wards, with evidence of cryptic transmission, and community-onset cases could not be identified in more than half the clusters, particularly on the elective hospital site, implicating HCW as vectors of transmission. Taken together these findings suggest that CSD had the dominant impact on reducing nosocomial transmission by reducing HCW infection.

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Nosocomial COVID-19: experience from a large acute NHS Trust in South-West London

Cited by 40 publications

References 3 publications

The burden of nosocomial covid-19: results from the Wales multi-centre retrospective observational study of 2518 hospitalised adults

The burden of nosocomial covid-19: results from the Wales multi-centre retrospective observational study of 2518 hospitalised adults

Estimating the effectiveness of routine asymptomatic PCR testing at different frequencies for the detection of SARS-CoV-2 infections

Combined epidemiological and genomic analysis of nosocomial SARS-CoV-2 transmission identifies community social distancing as the dominant intervention reducing outbreaks

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