The study—a collaboration between the London School of Hygiene & Tropical Medicine (LSHTM), Durham University, Medical Detection Dogs (MDD), and Arctech Innovation—comprised close to 4,000 volunteers across the United Kingdom, making it the most robust and in-depth trial of its kind in the world.
It set out to examine whether COVID-19 had an odor and, if so, whether it could be detected. The findings affirm positive answers to both questions.
Results show that dogs were able to distinguish between positive and negative odor samples with a sensitivity up to 94% and specificity up to 92%. Essentially, the dogs could identify which volunteers did and didn’t have the virus, meaning they are more accurate than lateral flow tests. And with the ability to screen some 300 people per hour, dogs are also considerably faster.
It makes canines an ideal screening tool at transport hubs, including airports. The dogs will indicate if they can smell the COVID-19 odor on an individual who would then need to take a confirmatory PCR test. The process would be fast, reliable, non-invasive, and will enable earlier self-isolation to prevent onward transmission.
In fact, mathematical modelling suggests that dog screening plus a confirmatory PCR test would avert up to 2.2 times as much transmission compared with the isolation of symptomatic individuals only.
“To correctly identify the odor over 94% of the time and to know when there was no disease present in over 90% of cases is remarkable,” says MDD Chief Scientific Officer, Dr Claire Guest. “It proves the positive impact that dogs, with their rapid turnaround time, could have for mass screening alongside a confirmatory PCR test as we continue to battle the pandemic. We believe that their noses could provide a strong line of defense against future pandemics.”
Dogs were an obvious tool to explore having proved their efficacy with several other diseases, including malaria. They are also a familiar sight at many transport hubs, usually checking for drugs or explosives.
“An important point is that dogs can detect very low levels of the virus,” says Professor James Logan, Department of Disease Control, LSHTM, and study lead. “It makes them very effective at screening mild and even asymptomatic cases.”
Detection is also specific to COVID-19. Professor Logan reveals that the dogs in the trial successfully ignored people who had cold symptoms but not COVID-19. More generally, canines are also a good deterrent and could prove effective at stopping people trying to fool the system.
“We wouldn’t envisage dogs at every gate in every terminal in the world,” says Professor Logan. “But you can target flights, perhaps with an algorithm that uses the difference in transmission rates between origin and destination countries. There is the potential to use dogs to screen pre- or post-flight or just use them generally in the airport environment. Whatever the situation, dogs could considerably speed up passenger throughput without any deterioration in risk management procedures.”
And with training taking just three months from scratch—much less if the dog is already skilled in odor detection—they could be deployed in the near future.
But as with any new diagnostic tool, a number of checks will be made. The next step of the study is testing the dogs in field conditions. This is not expected to produce significantly different results as the dogs are trained to ignore distractions and focus on the job at hand.
“Dogs can do this,” Professor Logan insists. “That is the whole point of the study. People will be confident with dogs sniffing. It is a passive, calm measure.”
Logan reports that airlines and airports are receptive to the idea of dogs screening for COVID-19 as is the World Health Organization (WHO). Indeed, WHO is developing guidelines for how dogs can be used not only for COVID-19 but also in any future pandemic.
“We wanted to demonstrate that dogs could be an effective screening tool for COVID-19 with robust science and a phased approach,” concludes Professor Logan. “The study has been done systematically so that everybody can see the results every step of the way. We believe we have a compelling story. Our findings demonstrate that people infected with SARS-CoV-2, with asymptomatic or mild symptoms, have a distinct odor that can be identified by trained dogs with a high degree of accuracy.”