‘Covid-19 has an odour, and the dogs are detecting it’: meet the canine super-squad sniffing out the virus

A single-storey building in a lonely rural business park, a few miles from Milton Keynes on a grey autumn day. It looks like a location for a bleak thriller: where a kidnap victim is held, perhaps, or the scene of a final shootout. Inside, though, something kind of cool is happening.In a brightly lit room, four inverted metal cups have been placed on the red carpet, each containing a small glass jar. One of these contains a smell: a “training odour”. Into the room bursts Billy, followed by Jess. Billy is a labrador, and Jess his human trainer. Billy bounces about the place, clearly super excited. He sniffs at everything – furniture, people, the cups – wagging ferociously. When he sniffs at the cup that contains the smell, another trainer, Jayde, indicates success with a clicking noise. Billy is rewarded with his favourite toy, a well-chewed rubber ball, and a chorus of “good boy”. So far, so unremarkable. Dogs have excellent noses, everyone knows that. They are estimated to be at least 10,000 times better than ours. It’s not immediately clear just how good Billy is. Did he really find the smell, or did Jayde just click when he sniffed the right cup? To be fair to Billy, he’s young, 18 months old, and this is only his second session. The trainers – Jess, Jayde and Mark – have high hopes for him. And after a couple more goes, it becomes clear that he is definitely finding the right cup, quickly. He is also clearly enjoying the game. What Billy lacks in refinement, he makes up for in youthful enthusiasm and exuberance, and he learns fast.
Which is good news: this is just the first stage for Billy, who is on a fast-track training course to learn to sniff out Covid-19. He’s not working with the actual virus, of course, but a training sample, which will teach him to do that job.
Trainer Jess with Belle, a two-year-old fox red labrador.Trainer Jess with Belle, a two-year-old fox red labrador. Photograph: Robert Ormerod/The Guardian
We are at the headquarters of Medical Detection Dogs, a charity co-founded by Claire Guest, a behavioural psychologist with a special interest in the relationship between people and dogs. She appears today with her own doggy entourage: cocker spaniel, wire-haired dachshund, a pair of labradors, all of which live with her and follow her around at work, like disciples. She chats to them: “No, no, no, Asher please… da-da-da, sweet pea!” Too late. Iggy, the dachshund, is a rescue dog and still learning things, including that the red carpet isn’t a toilet. Guest doesn’t blame him; it’s her fault, she says.

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It all started when a friend of Guest’s told her about her pet dalmatian sniffing persistently at one of her moles. The friend went to the GP, had the mole removed, and found she had a malignant melanoma. “From then on, I thought, if I can do anything in my life, I want to prove that dogs can smell cancer and disease,” says Guest. Later, she would have her own personal experience: a dog in training started to behave strangely around her, nudging her and staring at her as if concerned. Guest also went to the GP, was referred, “and to cut a long story short, I was diagnosed with early stage breast cancer”. It might sound more Take A Break magazine than the British Medical Journal, and Guest admits she has had to put up with a lot of scepticism along the way. But she points out that, back in 2004 she worked on the first scientific study that showed dogs can detect human bladder cancer, which was in fact published in the BMJ. Recently, she’s worked alongside Professors James Logan at the London School of Hygiene & Tropical Medicine, and Steve Lindsay of the department of biosciences at Durham University, among others, on a successful project to train dogs to identify malaria.Guest wasn’t surprised. “Dogs have 350m sensory receptors dedicated to olfaction, humans have 5m. Some dogs can work with parts per trillion.” Their research has indicated that these dogs can detect minuscule traces of odour, about one part per trillion, or the equivalent of a teaspoon in two Olympic swimming pools. When Covid-19 happened, Guest got to work again with Logan and Lindsay, both of whom I speak to by phone. First, though, there’s another dog to meet: Spencer, a golden retriever labrador cross, two years old. He came from the Guide Dogs charity, where they had noticed he was keener to use his nose than his eyes, (not what you want in a guide dog). Spencer has been training for a couple of weeks; he’s a slower learner than Bobby, says trainer Mark, certainly less bouncy. A bit of a plodder, I think, though he’ll get there in the end. And he does. Spencer correctly picks out the cups with the odour. Good boy.
The dogs in the photos, by Robert Ormerod, are not the same as the ones I’m meeting today. That’s because Ormerod visited Medical Detection Dogs before I did – and the dogs he photographed are further along in their training, in another part of the building where I can’t go because they are working not with a training odour (usually just a little piece of a dog’s favourite toy) but with the smell of actual Covid-19.
Asher, Belle, Tala and Florin training at Medical Detection Dogs.Asher, Belle, Tala and Florin training at Medical Detection Dogs. Photograph: Robert Ormerod/The Guardian
James Logan has been working in disease control for 20 years, and has a particular interest in the odour associated with disease. “We’ve known about this for hundreds of years. There are historic reports of medical professionals diagnosing people just by sniffing them,” he tells me. “Reports that yellow fever smells like a butcher’s shop, TB smells like stale brown bread.” More recently – and more scientifically – studies have demonstrated that respiratory viruses can be distinguished by the odour they cause the body to produce. “Viruses themselves do not produce odours. When the virus has infected our cells, this can have a knock-on effect on various systems within the body, which results in odours being released through our skin and breath. So there was a really strong likelihood that coronavirus would produce a distinct odour as well.”

Did you hear that? Sound frequency is measured in Hertz (Hz). The higher the Hertz, the higher-pitched the sound. Dogs hear best at 8,000 Hz, while humans hear best at around 2,000 Hz.

When the pandemic began, Logan got in touch with Guest, whom he had worked with on the malaria project. “I sent her a text saying, ‘I’ve got this idea of deploying dogs to detect Covid. What do you think? Do you think it’s crazy?’”
James Logan of the London School of Hygiene and Tropical Medicine and Claire Guest, co-founder of Medical Detection Dogs.James Logan of the London School of Hygiene and Tropical Medicine, and Claire Guest, co-founder of Medical Detection Dogs. Photograph: Robert Ormerod/The Guardian
Guest didn’t – she’d already been thinking about how the dogs might help. Nor, crucially, did the government think it was crazy; it has funded the project to the tune of half a million pounds. Lindsay came onboard again, to design the trial. He explains how it works. Samples are collected from hospitals, volunteers, people who test positive and develop symptoms of various degrees of severity, as well as asymptomatic cases. They wear socks, T-shirts and masks overnight, which go to Logan and his team for processing. Then the samples are sent on to Medical Detection Dogs to see if the dogs confirm what they had been hearing anecdotally from the wards: that Covid-19 has a smell. “Some people have described it as a sickly sweet smell,” says Logan.

In the stage that comes after the one I’m witnessing, the dogs pass along a line of metal stands, one of which will hold a positive Covid sample (sometimes there will be no positives, as there will sometimes be in the real world). Then the tests go double blind: not only are the dogs unaware which – if any – of the stands hold Covid-19 samples, so, too, are the handlers and everyone at Medical Detection Dogs.

Where is all this heading? “We are not looking to replace clinical testing,” Logan says. “We are keen to use dogs in very specific circumstances, where we need to get through a lot of people quickly. Airports, sports stadiums, train stations, universities, care homes.” Guest points out how useful it would have been to deploy Covid dogs at the airports early on in the pandemic, with all those flights coming here, bringing in so-called “super-spreaders” .

They’re not quite at the stage of releasing their results yet, but aim to publish as soon as there is enough data to robustly show how well dogs can detect coronavirus. There will be several independent reviews before anything is put into practice. But everyone – Guest, Lindsay, Logan, the trainers – is positive about the way the first phase, the proof-of-concept study, is going. “There is no doubt now that Covid has an odour, and the dogs are detecting it,” says Logan. The dogs will soon start to train with people, and in different situations – outside, in queues, crowds, including at an airport, hopefully Heathrow – says Logan. “It will be about getting the dogs working in an environment where there will be tannoy announcements and other distractions.” They hope this will happen early next year.

With all the brilliant news about vaccines and their efficacy, won’t the Covid dogs be redundant before they even get to work? Logan mentions “a readiness platform, for the next one. We know what to do, what samples we need, and how to collect them, so we can deal with this quicker next time.” If necessary, there could be a team of dogs, trained and ready to go, to sent out to an emerging virus’s country of origin.

Talk of “the next one” and “next time” is sobering. But Lindsay wasn’t surprised when this pandemic happened, and is already thinking about a similar outbreak in the future. “We have seen an increasing number of viruses and infections from animals spilling over to people,” he says.

Belle sniffs a training odour sample not containing real Covid-19.Belle sniffs a training odour not containing the actual virus. Photograph: Robert Ormerod/The Guardian

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Lindsay also points out that it’s going to take months to vaccinate everyone, and we don’t yet know how long immunity will last. “I hate to be a bit of a downer on this, but it might be that, as with flu vaccines, you get this genetic drift. We might need a different type of vaccine – it might always be behind.”

Guest knows how hard it is to roll out a mass vaccination programme: shehasn’t been able to get a flu jab this winter. “I think there’s going to be work for the dogs to do,” she says. Medical Detection Dogs is also collaborating with a quantum physicist at the Massachusetts Institute of Technology on developing electronic sensors to do the same work as the dogs, sniffing out disease (specifically prostate cancer), but that’s not currently up and running. Don’t stand the dogs down just yet, in other words. Speaking of which, I have one more to meet: another golden retriever labrador cross, Honey. She’s also two, but is a little further along in her training, working with clothes draped over the backs of chairs, arranged in a line. Honey walks with her trainer Jess down the line, sniffing. She’s at each chair for only a second or two; the same speed at which she would walk down a line of people at passport control, perhaps. At one chair, she sits – that’s how she indicates the item with the tell-tale odour. Is she right? Of course she is. And again, and again. She’s still working with a training odour, but Honey is ready to start on the real thing. Honey is adorable: calmer than Billy, cleverer than Spencer. When she sits, she looks up with a furrowed brow that appears to signify genuine concern. That’s better than a texted result, isn’t it? I can’t think of a nicer way of finding out you have Covid-19, than a golden dog sitting down with a frown?