̽��ֱ�� of Cambridge - William Hamilton

Hospital-acquired COVID-19 tends to be picked up from other patients, not from healthcare workers

cjb250 — Tue, 24 Aug 2021 07:00:25 +0000

̽��ֱ��study provides previously unprecedented detail on how infections might spread in a hospital context, showing that a minority of individuals can cause most of the transmission.

̽��ֱ��researchers analysed data from the first wave of the pandemic, between March and June 2020. While a great deal of effort is made to prevent the spread of viruses within hospital by keeping infected and non-infected individuals apart, this task is made more difficult during times when the number of infections is high. ̽��ֱ��high level of transmissibility of the virus and the potential for infected individuals to be asymptomatic both make this task particularly challenging.

Looking back at data from the first wave, researchers identified five wards at Addenbrooke’s Hospital, part of Cambridge ̽��ֱ�� Hospitals (CUH) NHS Foundation Trust, where multiple individuals, including patients and healthcare workers, tested positive for COVID-19 within a short space of time, suggesting that a local outbreak might have occurred.

Using new statistical methods that combine viral genome sequence data with clinical information about the locations of individuals, the researchers identified cases where the data were consistent with transmission occurring between individuals in the hospital. Looking in detail at these transmission events highlighted patterns in the data.

̽��ֱ��results of the study, published today in eLife, showed that patients who were infected in the hospital were mostly infected by other patients, rather than by hospital staff. Out of 22 cases where patients were infected in hospital, 20 of these were the result of the virus spreading from patients to other patients

Dr Chris Illingworth, a lead author on the study, who carried out his research while at Cambridge’s MRC Biostatistics Unit, said: “ ̽��ֱ��fact that the vast majority of infections were between patients suggests that measures taken by hospital staff to prevent staff transmitting the virus to patients, such as the wearing of masks, were likely to have been effective.

“But it also highlights why it is important that patients themselves are screened for COVID-19 regularly, even if asymptomatic, and wear face masks where possible.”

̽��ֱ��study found contrasting results among healthcare workers, who were almost as likely to be infected by patients as they were by other healthcare workers. This was one piece of evidence that motivated the decision to upgrade the respiratory protection worn by healthcare workers in COVID-19 wards at CUH. A recent Cambridge study indicated that this resulted in staff being better protected against catching COVID-19.

̽��ֱ��researchers also found a trend towards individuals either infecting no one else, or infecting multiple other people – just over a fifth of patients (21%) caused 80% of the infections. This phenomenon is sometimes called ‘superspreading’ and can make infection control very challenging. Whether or not an individual can be identified in advance as being more or less likely to pass on the virus is an ongoing topic of research.

Dr William Hamilton, an infectious diseases clinician at CUH and co-lead author on the study said: “Preventing new cases of hospital-based infection is a critical part of our work. Here we have shown that analysing clinical and viral genome sequence data can produce insights that inform infection control measures, which are so important for protecting patients and healthcare workers alike.”

̽��ֱ��research was funded by COG-UK, Wellcome, the Academy of Medical Sciences, the Health Foundation and the NIHR Cambridge Biomedical Research Centre.

Reference
Illingworth, CJR & Hamilton, WL et al. Superspreaders drive the largest outbreaks of hospital onset COVID-19 infections. eLife; 24 Aug 2021; DOI: 10.7554/eLife.67308

̽��ֱ��majority of patients who contracted COVID-19 while in hospital did so from other patients rather than from healthcare workers, concludes a new study from researchers at the ̽��ֱ�� of Cambridge and Addenbrooke’s Hospital.

̽��ֱ��fact that the vast majority of infections were between patients suggests that measures taken by hospital staff to prevent staff transmitting the virus to patients, such as the wearing of masks, were likely to have been effective

Chris Illingworth

Preventing hospital acquired Covid-19 infection | Estée Torok

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Coronavirus

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Genomics study identifies routes of transmission of coronavirus in care homes

cjb250 — Wed, 03 Mar 2021 09:27:53 +0000

Care homes are at high risk of experiencing outbreaks of COVID-19, the disease caused by SARS-CoV-2. Older people and those affected by heart disease, respiratory disease and type 2 diabetes – all of which increase with age – are at greatest risk of severe disease and even death, making the care home population especially vulnerable.

Care homes are known to be high-risk settings for infectious diseases, owing to a combination of the underlying vulnerability of residents who are often frail and elderly, the shared living environment with multiple communal spaces, and the high number of contacts between residents, staff and visitors in an enclosed space.

In research published today in eLife, a team led by scientists at the ̽��ֱ�� of Cambridge and Wellcome Sanger Institute used a combination of genome sequencing and detailed epidemiological information to examine the impact of COVID-19 on care homes and to look at how the virus spreads in these settings.

SARS-CoV-2 is an RNA virus and as such its genetic code is prone to errors each time it replicates. It is currently estimated that the virus mutates at a rate of 2.5 nucleotides (the A, C, G and U of its genetic code) per month. Reading – or ‘sequencing’ – the genetic code of the virus can provide valuable information on its biology and transmission. It allows researchers to create ‘family trees’ – known as phylogenetic trees – that show how samples relate to each other.

Scientists and clinicians in Cambridge have pioneered the use of genome sequencing and epidemiological information to trace outbreaks and transmission networks in hospitals and community-based healthcare settings, helping inform infection control measures and break the chains of transmission. Since March 2020, they have been applying this method to SARS-CoV-2 as part of the COVID-19 Genomics UK (COG-UK) Consortium.

In this new study, researchers analysed samples collected from 6,600 patients between 26 February and 10 May 2020 and tested at the Public Health England (PHE) Laboratory in Cambridge. Out of all the cases, 1,167 (18%) were care home residents from 337 care homes, 193 of which were residential homes and 144 nursing homes, the majority in the East of England. ̽��ֱ��median age of care home residents was 86 years.

While the median number of cases per care home was two, the ten care homes with the largest number of cases accounted for 164 cases. There was a slight trend for nursing homes to have more cases per home than residential homes, with a median of three cases.

Compared with non-care home residents admitted to hospital with COVID-19, hospitalised care home residents were less likely to be admitted to intensive care units (less than 7% versus 21%) and more likely to die (47% versus 20%).

̽��ֱ��researchers also explored links between care homes and hospitals. 68% of care home residents were admitted to hospital during the study period. 57% were admitted with COVID-19, 6% of cases had suspected hospital-acquired infection, and 33% were discharged from hospital within 7 days of a positive test. These findings highlight the ample opportunities for SARS-CoV-2 transmission between hospital and care home settings.

When the researchers examined the viral sequences, they found that for several of the care homes with the highest number of cases, all of the cases clustered closely together on a phylogenetic tree with either identical genomes or just one base pair difference. This was consistent with a single outbreak spreading within the care home.

By contrast, for several other care homes, cases were distributed across the phylogenetic tree, with more widespread genetic differences, suggesting that each of these cases was independent and not related to a shared transmission source.

“Older people, particularly those in care homes who may be frail, are at particular risk from COVID-19, so it’s essential we do all that we can to protect them,” said Dr Estée Török, an Honorary Consultant at Addenbrooke's Hospital, Cambridge ̽��ֱ�� Hospitals (CUH), and an Honorary Senior Visiting Fellow at the ̽��ֱ�� of Cambridge.

“Preventing the introduction of new infections into care homes should be a key priority to limit outbreaks, alongside infection control efforts to limit transmission within care homes, including once an outbreak has been identified.”

̽��ֱ��team found two clusters that were linked to healthcare workers. One of these involved care home residents, a carer from that home and another from an unknown care home, paramedics and people living with them. ̽��ֱ��second involved several care home residents and acute medical staff at Cambridge ̽��ֱ�� Hospitals NHS Foundation Trust who cared for at least one of the residents. It was not possible to say where these clusters originated from and how the virus spread.

“Using this technique of ‘genomic surveillance’ can help institutions such as care homes and hospitals better understand the transmission networks that allow the spread of COVID-19,” added Dr William Hamilton from the ̽��ֱ�� of Cambridge and CUH. “This can then inform infection control measures, helping ensure that these places are as safe as possible for residents, patients, staff and visitors.”

̽��ֱ��absolute number of diagnosed COVID-19 cases from care home residents declined more slowly in April than for non-care home residents, increasing the proportion of cases from care homes and contributing to the slow rate of decline in total case numbers during April and early May 2020.

“Our data suggest that care home transmission was more resistant to lockdown measures than non-care home settings. This may reflect the underlying vulnerability of the care home population, and the infection control challenges of nursing multiple residents who may also share communal living spaces,” said Gerry Tonkin-Hill from the Wellcome Sanger Institute.

̽��ֱ��team found no new viral lineages from outside the UK, which may reflect the success of travel restrictions in limiting new viral introductions into the general population during the first epidemic wave and lockdown period.

This work was funded by COG-UK, Wellcome, the Academy of Medical Sciences, the Health Foundation and the NIHR Cambridge Biomedical Research Centre.

Reference
Hamilton, W et al. COVID-19 infection dynamics in care homes in the East of England: a retrospective genomic epidemiology study. eLife; 2 March 2021; DIO: 10.7554/eLife.64618

Genomic surveillance – using information about genetic differences between virus samples – can help identify how SARS-CoV-2 spreads in care home settings, whose residents are at particular risk, according to new research published today.

Older people, particularly those in care homes who may be frail, are at particular risk from COVID-19, so it’s essential we do all that we can to protect them

Estee Torok

National Cancer Institute

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