Hospital staff carrying COVID-19

12 May 2020

CORONAVIRUS

A stylised coronavirus particle next to a woman wearing a facemask.

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Hospital staff are carrying COVID-19 without realising they’re infected, a new study by researchers at the University of Cambridge has shown...

Patients admitted to NHS hospitals are now routinely screened for the Covid-19 virus, and isolated if necessary. But NHS workers, including patient-facing staff on the front line like doctors, nurses and physiotherapists, are tested and excluded from work only if they develop symptoms of the illness. Many of them, however, as  a new study published today in the journal eLife demonstrates, may show no symptoms at all.

The Cambridge team pro-actively swabbed and tested over 1200 NHS staff at Addenbrooke’s Hospital across April. The samples were analysed using a technique called PCR to copy and read the genetic information of the Covid-19 virus, producing a colour change whenever the virus was present in a specimen. At the same time, staff members were asked about relevant coronavirus symptoms.

Of the more than 1000 staff members reporting fit for duty during the study period, 3% nevertheless tested positive for the Covid-19 virus. On closer questioning, about half of them admitted to vague symptoms that they had dismissed as inconsequential, and a quarter confirmed remaining symptom-free throughout .

To probe routes of possible transmission of the virus through the hospital and among staff, the project also looked at whether rates of infection were greater among staff working in “red” areas of the hospital caring for Covid-19 infected patients. Despite wearing appropriate personal protective equipment (PPE), “red” area staff tested positive threefold more often than staff working in Covid-19-free “green” areas.

It’s not clear whether this genuinely reflects greater rates of transmission from patients to staff in red areas. Staff may have instead transmitted the virus to each other, or acquired it at home. And staff working in the “red” areas were also swabbed earlier in the study, closer to when the lockdown was first initiated, so the higher rates of infection in this group might just be a symptom of higher rates of virus circulating in the community at the time.

Nevertheless, extrapolating these results to the more than half a million patient-facing staff working across the NHS UK-wide suggests that as many as 15,000 workers may have been on duty and infected, with the potential to transmit the virus to co-workers, family members and patients, during the month of April.

The implications of the new study, say senior authors Mike Weekes and Steve Baker, are that hospitals need to be vigilant and introduce screening programmes across their workforces.  “Test! Test! Test! And then test some more,” Weekes explains. “All staff need to get tested regularly for COVID19, regardless of whether they have any sort of symptoms – this will be vital to stop infection spreading within the hospital setting.”

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