RESEARCHERS have warned that “wide variation” in the spread of Covid in UK hospitals needs further investigation, with a quarter of infected patients in some acute sites contracting the virus after admission during the first wave of the pandemic.

Experts blamed shortages of PPE, a lack of testing capacity, and confusion over Covid symptoms for contributing to higher rates of hospital-acquired conronavirus earlier in the outbreak.

Evidence published today in the Lancet estimates that, overall, 11.3 per cent of the Covid positive patients in hospital up to August 1 2020 had become infected following admission, based on date of symptom onset and the incubation period of the virus.

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However, there was "marked heterogeneity" between NHS hospitals and depending on the type of care they provided.

Hospitals providing acute and general care had a lower proportion of hospital-onset Covid cases - at 9.7% on average - but this ranged from 1% to 25% between the best and worst performing sites.

Meanwhile, in mental health hospitals and residential community care facilities, 67.5% and 61.9% respectively of the Covid cases detected among their patients were estimated to have been contracted on-site, reflecting the higher levels of long-stay patients who would have fewer opportunities to be exposed in the community.

HeraldScotland: The percentage of Covid cases being contracted in hospital peaked in mid- to late-May, two months after total the number of Covid patients in hospital peakedThe percentage of Covid cases being contracted in hospital peaked in mid- to late-May, two months after total the number of Covid patients in hospital peaked

Professor Calum Semple, an expert in outbreak medicine who contributed to the research, said it a figure of around 10% for hospital-acquired infections would be expected in the case of pandemic influenza and was "not surprising in the round" for a coronavirus.

He added: "What is interesting is the variation. We would expect long-term residential facilities to be higher because people stay in them longer.

"But if you were just to look at the acute/general hospitals, your typical district general hospital, you'll see that there was substantial variation even within hospitals that were busy, that had literally thousands of patients coming in.

"There were some outstanding examples of good infection prevention control and there were some examples where that was not good.

"We think there is a number of factors - PPE is one. We know that there were challenges around PPE at the start of the outbreak.

"We also know that the mode of transmission was poorly understood at the start of the outbreak. We know that at least one in 20 patients were admitted with purely abdominal and enteric features - vomiting, diarrhoea, abdominal pain - would have been misclassified as non-Covid patients at the start of the outbreak because they didn't have classic Covid.

"We didn't have access to accurate testing at the start of the outbreak, so there was a lot of things that could go wrong."

HeraldScotland: A higher percentage of Covid cases in residential and mental health facilities were contracted on site, compared to acute/general hospitals where patients were more likely to have been exposed prior to admissionA higher percentage of Covid cases in residential and mental health facilities were contracted on site, compared to acute/general hospitals where patients were more likely to have been exposed prior to admission

The study was led by Lancaster University with input from Edinburgh, Liverpool, Imperial and Birmingham universities.

The findings are based on analysis of 72,157 people diagnosed with Covid who were treated at 314 UK hospitals during the first wave, representing two thirds of all known Covid hospital patients during that time.

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The data on the best and worst performing hospitals has been shared with the NHS but will not be made public.

"This is about quality improvement, not a blame game," said Prof Semple.

He added that during the current third wave of Covid, around 2-5% of patients in hospital with the infection in the UK had become infected post-admission.

HeraldScotland: Professor Calum SempleProfessor Calum Semple

Dr Annemarie Docherty, a critical care medic and co-author on the study from Edinburgh University, said increased availability of testing "has been a game-changer" in curbing hospital spread.

She said: "Now we have reliable tests in the emergency department that can be back within the hour so then we know whether the patient has Covid or not and then we can get them to the appropriate place."

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Co-author Dr Chris Green said that, once adjusted for age and sex, patients who acquired Covid in hospital had slightly lower death rates compared to those who contracted the virus in the community and were then subsequently admitted to hospital.

He said this was probably a reflection of receiving "extremely good care" quickly.

Prof Semple added: "Lessons were learned and things have got better, but there will be tragedies behind this story. We do know of people who came into hospital for one problem, caught coronavirus and sadly died.

"One cannot minimise the tragedies that occurred."