COVID odour in socks detectable by dogs

A new study shows that trained dogs are highly accurate at smelling COVID
03 June 2021

Interview with 

Claire Guest, Medical Detection Dogs


A close up of a dog's nose


Help to control COVID-19 might come in future in the unlikely form of “man’s best friend”. Claire Guest is the chief scientific officer at Medical Detection Dogs, where dogs are trained to sniff out human diseases ranging from malaria and C. diff through to bladder cancer. Now Claire and her team have turned their attention, and their noses, to COVID, with remarkable results, as she told Eva Higginbotham...

Claire - Without any question when somebody has COVID-19 and interestingly that's whether or not they're asymptomatic or have symptoms, there is clearly a definite odor that a dog can be trained to recognise. Now, the interesting thing is for this first proof of concept study, we were training dogs to detect the odour on a piece of clothing that had been worn by an individual. So actually it's a sock. So individuals were asked to wear a sock for 12 hours, and then after several weeks, the dogs were asked to see if they could distinguish the odor by sniffing the sock. And they were still able to do it with remarkable accuracy. And this of course is incredibly exciting.

Eva - Puts the idea of smelly socks into a whole new context.

Claire - Doesn't, it indeed. Absolutely. I mean, we sweat a lot through our feet and having worked in other diseases, for example, malaria, we find that we get a very good signal of these particular socks. So that's where we started and we found the same.

Eva - And all the dogs smelling the disease itself, or are they smelling something a human makes in response to having COVID and somehow exudes.

Claire - So it's not the virus itself in terms of, you know, the dog is not trained to find the virus on a contaminated surface. What the dog is doing is finding an individual whose body has responded to the effects of the virus. But as I mentioned previously, the very exciting and interesting thing is that the person doesn't have to be symptomatic. So the effects of the virus on the body is being detected by the dogs, regardless of whether that individual has symptoms or not.

Eva - And how accurate are the dogs that you've trained at identifying a coronavirus sock versus a non coronavirus sock, and also compared to another kind of coronavirus. Because the coronavirus that causes COVID is of course only one, there are many coronaviruses.

Claire - So the dogs were able to detect coronavirus when an individual had just some sniffing, as I say, a sock worn several weeks ago, up to 94% reliability. That's 94% sensitivity. They were also able to reliably identify if somebody hadn't got the virus specificity up to 92%. So we're talking a very, very accurate test here. And if we compare that say with a lateral flow test, which are currently being used, the dogs are much, much more accurate. So the other very interesting finding was that the dog's ability to detect viruses was not affected by viral loads. Now, when you compare it to something like the lateral flow test, this has become very unreliable as the viral load becomes lower. Now, again, this is very, very interesting, and it means that in the future, these dogs could be used to identify viruses and people who are presymptomatic, so in the early stages of viral load and this is, you know, it could be, have a huge impact.

Eva - And do you know what it is that it's actually smelling, what chemical or molecule in the sweat means you have coronavirus.

Claire - We don't know exactly yet what it is. But the team at London School of Hygiene and Tropical Medicine have been doing some analysis on the volatile pattern of coronavirus at the same time. And what we have seen is that the samples identified by the dogs are showing volatile patterns that are quite distinct. This is very exciting and could lead to not only dogs working in the future, but perhaps some sort of electronic analyser.

Eva - Like an artificial nose that could smell diseases.

Claire - Absolutely. I mean, the challenge is that the dog is an incredibly good pattern recogniser. And it's a bit like if I, I'm going to sing incredibly badly now, but if I say dah, dah, dah, you immediately recognise that. And although I'm not an orchestra, you still recognize the tune. Now what the dogs are really incredible at doing is recognising tunes. Now at the moment, electronic sensors need to know the exact notes and the amount of notes to get the detection correct. Whereas the dogs can listen to a pattern and say, listen in a sort of listen to what their nose is saying, that that is the same pattern. That's why they're so good at this type of work at the moment.



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