A recent study by the University of Helsinki and Helsinki University Hospital confirmed that scent detection dogs can be taught to identify individuals with a coronavirus infection from skin swabs. In the experimental set-up at Helsinki-Vantaa International Airport in Finland, the accuracy of the scent detection dogs to identify the samples was 92 percent.

Rapid and accurate identification and isolation of patients with coronavirus infection is an important part of global pandemic management. The current diagnosis of coronavirus infection is based on a PCR test that accurately and sensitively identifies coronavirus from other pathogens. However, PCR tests are ill-suited for screening large masses of people due to, among other things, their slow results and high cost.

Researchers from the Faculties of Veterinary Medicine and Medicine at the University of Helsinki and the Helsinki University Hospital jointly designed a triple-blind, randomized, controlled study set-up to test the accuracy of trained scent detection dogs where none of the trio – dog, dog handler or researcher – knew which of the sniffed skin swab samples were positive and which negative. The study also analyzed factors possibly interfering with the ability of the dogs to recognize a positive sample.

The three-faceted study has now been published in the journal BMJ Global Health. The study provides valuable information on the use of scent detection dogs in pandemic control.

Correct sample identification percent over 90, only small differences in accuracy between dogs

In the first phase of the study, the scent detection dogs were taught to discriminate the skin swab samples of coronavirus patients from samples of volunteers tested negative. After a training period of several weeks, the scent detection dogs moved from the dog training center to Helsinki-Vantaa Airport (Finland) for the next stages of the study.

In the second phase of the study, four trained scent detection dogs completed a validation test, proving their discrimination ability. During the experiment, each dog was presented with a series of 420 samples over a period of seven testing days. Several parallel samples had been collected from each sample donor, so each dog received an identical set of 114 coronavirus patient samples and 306 control samples for sniffing. The coronavirus status of all sample donors had been confirmed by PCR. During each testing day, the dog sniffed 20 sample tracks with three samples each, the tracks presented in random order.

The dogs recognized the samples correctly 92 percent of the time. Their sensitivity to detect a positive coronavirus sample was 92 percent and their specificity was 91 percent. Only small differences in accuracy were observed between the four dogs. The coronavirus infection caused by virus variants was the single largest factor contributing to an erroneous identification by the trained corona dogs.

The study confirms previous reports suggesting that scent detection dogs can identify those with a coronavirus infection.

– Our study set-up was of high scientific quality. The sample sizes were large enough, and all dogs sniffed an identical set of samples, allowing the dogs performances to be compared. The dogs also had to successfully indicate sample sets containing only negative samples, an important trait when screening individuals. A significant advantage was also that samples were collected from outpatients instead of hospital patients. In addition, the testing was performed under real-life conditions and not in a laboratory, describes the leader of the DogRisk research group and docent of clinical research in companion animals Anna Hielm-Björkman from the University of Helsinki.

– I was particularly impressed by the fact that dogs performed worse with samples we had collected from patients suffering from a disease caused by a corona virus variant. The explanation is simple: the dogs had initially been trained with the initial wild-type virus, and thus they did not always identify the variant samples as positive. This reveals their incredible discrimination ability, says Anu Kantele, Professor of Infectious Diseases and Chief Physician at the University of Helsinki and Helsinki University Hospital.

Major help from scent dogs at airports and ports

The third phase of the study was conducted by screening passengers and staff at Helsinki-Vantaa Airport in a “real-life” situation. The scent dogs correctly identified 98.7 percent of the negative samples. The low number of coronavirus-positive samples in the real-life testing prevented a proper assessment of the dogs’ performance on the positive samples. However, based on positive “work motivation samples” regularly given to the dogs during this part of the study, the performance on the correctly identified positive samples was also evaluated at 98.7 percent. Work motivation samples are naive samples pre-collected from PCR positive patients, but never sniffed by dogs before. They are provided to the dogs at regular intervals to motivate them to keep on looking for the target odor in situations and environments where the proportion of positive samples is otherwise very low.

– Scent detection dogs can provide an invaluable tool for limiting the spread of a virus during a pandemic, serving for example at airports and ports. Such a reliable, cheap approach to rapidly screen a vast number of samples or to identify by-passing virus carriers from a large crowd is of particular value when the testing capacity with traditional approaches is insufficient, says Anu Kantele.

– Our research group will continue to study how scent detection dogs best can help our society. We hope that this newly published study will help to allocate funds for the development of this new “tool”. There are many other diseases where research could benefit from the excellent sense of smell that these scent detection dogs possess, says Hielm-Björkman.

The study was conducted with the support of the Finnish Cultural Foundation, Svenska Kulturfonden i Finland, Academy of Finland, Jane and Aatos Erkko Foundation, Finnish Medical Association, Veterinary Hospital Chain Evidensia, Nose Academy, Finavia, Vantaa city and deputy mayor Timo Aronkytö. The research group of Anna Hielm-Björkman has also been supported by private donations through the coronadog fundraising campaign, organized jointly by the Finnish Kennel Club and the University of Helsinki. The dogs were initially trained at the NGO Wise Nose trainings center.


Original article: Kantele A, Paajanen J, Turunen S, Pakkanen S, Mattress A, Itkonen L, Heiskanen E, Lappalainen M, Desquilbet L, Vapalahti O, Hielm-Björkman A. Scent dogs in detection of COVID-19 – triple-blinded randomized trial and operational real -life screening in airport setting . BMJ – Global Health, 2022; 0: e008024. Doi : 10.1136/bmjgh-2021-008024

Watch videos of one validation session of one dog and how the validation was done here:


More information:

Anu Kantele, Professor of Infectious Diseases, University of Helsinki

Chief Physician, Helsinki University Hospital
Tel. + 358- (0) 50-3097640

Anna Hielm-Björkman, leader of the DogRisk research group, docent of clinical research in companion animals, University of Helsinki

Tel. + 358- (0) 44-3270462


DogRisk link: