Canine v COVID-19: The Smell of SARS-CoV-2

Just as garlic has a distinct smell due to its chemical compounds, COVID-19 also exudes a perceptible scent, not to humans though, but to their best friend, dogs.

Airports from all around the world have been using dogs to sniff out COVID-19. Recently, Finland’s Helsinki-Vantaa airport has deployed detection dogs to screen passengers infected with the coronavirus.

Kössi, a coronavirus sniffer dog, at Finland's Helsinki-Vantaa airprt. PHOTO FROM: Antti Aimo-Koivisto

With a state-funded pilot scheme for canine testing in the airport, sweat from passengers is collected which would then be placed next to a beaker with the control scent and the dogs would then signal– shown by yelping, pawing, or lying down – if the person has the virus. The person takes a free swab test to verify its verdict.

Furthermore, running a pilot study at the University of Helsinki, researchers Anna Hielm-Björkman and Anu Kantele discover that the dogs can also distinguish urine samples from COVID-19 patients from those from healthy individuals

“It was fantastic to see how fast the dogs took to the new smell,” Hielm-Björkman says.

Additionally, countries from the UK to Spain, Brazil, Lebanon, and Australia have used dogs as a viable way to detect the virus. The United Arab Emirates (UAE) airports have also been using canine testing for the virus since August.

In a study conducted by Professor Dominique Grandjean, of the National Veterinary School of Alfort in France, results show that dogs correctly identify the COVID-19 patients at least 83% of the time with some dogs going 100% all through the trials. The results have yet to be peer-reviewed as well as validations from three separate trials yet to be published

On how they detect the disease, dogs do not inhale the viruses themselves but rather the tell-tale signs of volatile chemicals produced when the virus infects cells. The dogs undergo scent-training to be able to detect the low concentrations of volatile organic compounds associated with COVID-19 according to Grandjean.

Even before the pandemic, dogs are used in bomb detection, search & rescue, and even cancer detection. The dog’s sense of smell is about one thousand times more powerful than a human’s, due to their proportionally bigger noses having a larger surface area containing olfactory mucosa/lining. According to veterinary surgeon Gudi Stuttard, dogs have two to 300 million olfactory receptors to be able to detect the odors, compared to human’s six million.

Despite the dog’s high sense of smell, the biomarker, metabolites, or scent molecules for the COVID-19 detection is still unsure, sparking issues with the testing method’s specificity to the virus

Saying that these initiatives would only derail the prospects of mass testing, Professor Ian Jones, a virologist at the University of Reading, has said that the only thing dogs can detect is the odor difference. Different viruses attack the same cells and would lead to similar changes to metabolism, meaning that other viruses may exude the same smell of SARS-CoV-2.

However, Grandjean was optimistic about their findings saying that different types of viruses have different volatile organic compounds coming from cell cultures, meaning chemical compounds are specific to each virus. Nevertheless, this had yet to be proved for SARS-CoV-2.