Covid-19 infection has a distinct smell that can be detected by specially trained dogs with up to 94% accuracy, UK research suggests.
The findings, which have not yet been peer-reviewed, are based on six dogs who tested more than 3,500 odour samples donated by the public and NHS staff.
The canines were able to sniff out samples from people who were infected with coronavirus but were asymptomatic, as well as those who had low viral loads.
They were also able to identify infections caused by the coronavirus strain that was dominant in the UK last summer as well as the UK (Kent) version of the virus which appeared later in the year.
Professor James Logan, head of the department of disease control at London School of Hygiene and Tropical Medicine (LSHTM), who led the project, said: “What was great was the dogs that have been trained on the original variant transferred to the new (Kent) variant.
“They could detect the new variant without any additional training.
“So this gives us real hope and really suggests that dogs are able to detect different variants of Covid.”
Six dogs – Asher, Kyp, Lexie, Tala, Millie, and Marlow – from the charity Medical Detection Dogs took part in the double-blind trial.
This means neither the research team nor the dogs knew which of the odour samples came from those infected with Covid-19 and which were coronavirus-free.
The research, which was part-funded by the UK’s Department of Health and Social Care, showed that the specially trained dogs were able to quickly detect coronavirus-infected samples with up to 94.3% sensitivity (the ability to correctly identify positive cases) and up to 92% specificity (the ability to correctly identify negative cases).
The scientists said the next phase of the trial will test whether these “super sniffers” are able to detect coronavirus on real people in real-world settings such as airports and sports events.
Meanwhile, preliminary analysis using mathematical modelling suggests two dogs could screen 300 plane passengers in half an hour.
The researchers said using a rapid screen and test strategy, individuals who are identified by the dogs would then require a PCR test to confirm diagnosis.
They believe a combination of specially trained dogs, along with a confirmatory PCR test, could help detect more than twice as many cases and halt onward transmission, when compared to isolating symptomatic individuals only, or testing people with a lateral flow test and a PCR test.
Professor Steve Lindsay, from the department of biosciences at Durham University, said: “This is a very exciting result showing that there is a distinct smell associated with Covid-19 and, more importantly, that trained dogs can detect this with a high degree of accuracy.
“Dogs could be a great way to screen a large number of people quickly and preventing Covid-19 from being reintroduced into the UK.
“Trained dogs could potentially act as a fast screening tool for travellers, with those identified as infective confirmed with a lab test.
“This could make testing faster and save money.”
Dr Claire Guest, chief scientific officer at Medical Detection Dogs, said: “These fantastic results are further evidence that dogs are one of the most reliable biosensors for detecting the odour of human disease.
“Our robust study shows the huge potential for dogs to help in the fight against Covid-19.”