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

Date:
August 24, 2021
Source:
University of Cambridge
Summary:
The majority of patients who contracted COVID-19 while in hospital
did so from other patients rather than from healthcare workers,
concludes a new study.



FULL STORY ==========================================================================
The 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 University of Cambridge and Addenbrooke's Hospital.


==========================================================================
The 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.

The 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. The 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 University 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.

The 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: "The 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." The 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.

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

========================================================================== Story Source: Materials provided by University_of_Cambridge. The original
text of this story is licensed under a Creative_Commons_License. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Christopher JR Illingworth, William L Hamilton, Ben Warne, Matthew
Routledge, Ashley Popay, Chris Jackson, Tom Fieldman, Luke W
Meredith, Charlotte J Houldcroft, Myra Hosmillo, Aminu S Jahun,
Laura G Caller, Sarah L Caddy, Anna Yakovleva, Grant Hall, Fahad
A Khokhar, Theresa Feltwell, Malte L Pinckert, Iliana Georgana,
Yasmin Chaudhry, Martin D Curran, Surendra Parmar, Dominic Sparkes,
Lucy Rivett, Nick K Jones, Sushmita Sridhar, Sally Forrest, Tom
Dymond, Kayleigh Grainger, Chris Workman, Mark Ferris, Effrossyni
Gkrania-Klotsas, Nicholas M Brown, Michael P Weekes, Stephen
Baker, Sharon J Peacock, Ian G Goodfellow, Theodore Gouliouris,
Daniela de Angelis, M Este'e To"ro"k. Superspreaders drive the
largest outbreaks of hospital onset COVID-19 infections. eLife,
2021; 10 DOI: 10.7554/eLife.67308 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210824083504.htm

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