Screening healthcare workers for Covid-19

"Stay home, stay safe, protect the NHS" has been one of the UK government’s strategies to control the spread of coronavirus. But what about in hospitals themselves? Patients with the infection are of course being treated there, and staff need to come to work to look after them. It's, naturally, much harder to maintain social distancing in healthcare settings too. So how many staff are infected with the virus? Surprisingly, until Cambridge University Infectious Diseases consultant Mike Weekes and microbiologist Steve Baker set up a project to find out - by screening over a thousand healthcare workers at Addenbrooke's, the University of Cambridge teaching hospital -  no one knew. Speaking with Chris Smith, Mike Weekes first…

Mike - It's obviously a huge issue because staff within the hospital could transmit the infection to other staff and to patients, and actually hospitals could become their own individual hubs of transmission unless we do something about it. Staff wear PPE throughout the wards, but obviously people don't wear PPE in staff rooms; they don't wear PPE when they go to lunch, because you can't; and so there's the possibility that the virus could transmit. We got our infectious diseases team to visit different wards around the hospital, and take swabs from people's throats and noses, so that they could go to Steve's lab and we could see if they actually had coronavirus.

Chris - You got these samples from all over the hospital. How many samples did you get, Steve?

Steve - At the moment I think we've screened about two and a half to three thousand individuals in the hospital.

Chris - How long does this take?

Steve - The whole process from the point that we can receive the swabs, to we can report back - the quickest we've done it is about four hours. Usually we report back a result within 24 hours.

Chris - And Mike, you've looked at these staff members. What did you find?

Mike - It's really interesting. We actually found that three in a hundred people tested positive for coronavirus, and actually these people were split into three groups. The first is people who have no symptoms at all, and so they just have no idea they have the coronavirus. The second is a group of people who've had mild symptoms, like a bit of a cough, a sore throat, some have even lost their sense of smell; and they don't think that they have enough symptoms to warrant doing anything about, in general. The final group we found, actually, had had coronavirus a long time ago; and they'd had fever and a prolonged cough, the typical symptoms, and they appropriately self isolated at home and then came back to work when they were well. You can still test positive even though you shouldn't be infectious.

Chris - The fact that these people are not reporting symptoms is worrying though, isn't it? Because we're relying on symptoms to detect who we think might have it in society.

Mike - You're quite right. Unfortunately this is one of the features of coronavirus, that some people just have no symptoms; and some people's symptoms are so minor, they just don't think they should do anything about it. But we're really encouraging staff now to come and see us, so they can get tested if they have any symptoms.

Chris - Hospitals are seeking to control this by dividing the hospital up into areas that are red, they have patients in them with coronavirus as a diagnosis, confirmed; there are also areas of the hospital which are regarded as green, those people don't have coronavirus. If you look at the staff who work in those different areas, are there any differences in the likelihood that they've got coronavirus infection, because they're being exposed more in red areas? Do they catch it more?

Mike - We did actually find a significant difference between red and green areas. In red areas a greater proportion of staff actually do have coronavirus overall, but it might be because staff are getting it from patients. It might be staff getting it from staff, or it might even be that we'd sampled more of the red areas a bit earlier. We sampled over the course of three weeks, but as everyone had been on lockdown, there were fewer and fewer cases in the community. We can't make any firm conclusions from this, but what we can definitely say is that this needs to be studied a lot more.

Chris - What if you're asked by the hospital, "right? What do we do with these findings? What are your advice points?"

Mike - Test, test, test, and then test again. Because the kind of approaches we can apply in the community, like these contact tracing apps on iPhones, won't necessarily work in hospitals because so many people have contact with other people.