Unsplash | John Tuesday

Trained dogs are reliable for detecting Covid-19 cases, and maybe even better than PCR tests for identifying asymptomatic cases. A bonus: The canines are cuter and less invasive than a swab up the nose.

In a study involving sweat samples from 335 people, trained dogs sniffed out 97 percent of  the coronavirus cases that had been identified by PCR tests, researchers report June 1 in PLOS One. And the dogs found all 31 Covid-19 cases among 192 people who didn’t have symptoms.

These findings are evidence that dogs could be effective for mass screening efforts at places such as airports or concerts and may provide friendly alternatives for testing people who balk at nasal swabs, Dominique Grandjean a veterinarian at the National School of Veterinary Medicine of Alfort in Maisons-Alfort, France, tells Science News.


Each pup was rewarded with toys if they picked out the virus successfully in sweat samples

Anecdotal evidence also suggested that dogs can pick up asymptomatic cases 48 hours before individuals test positive in PCR tests, reports Tina Hesman Saey for Science News. However, the dogs at times mistook another respiratory virus for SARS-CoV-2. The authors did not seem concerned with these cases—of the 17 false positives (cases where dogs mistakenly thought a sample was positive for SARS-CoV-2), only two were positive for another respiratory virus, though both cases were another kind of coronavirus.

For the study, the researchers used dogs from French fire departments and the Ministry of the Interior of the United Arab Emirates. Each pup was rewarded with toys like tennis balls if they picked out the virus successfully in sweat samples. The training took anywhere between three to six weeks, depending on the dog's experiences with odor detection, per Science News.


Don’t try this at home

Per Science News, while dogs could detect Covid cases, researchers still are unsure what the dogs are specifically smelling. Instead of one single chemical, it can be a mixture of decreasing or increasing aromas—receptors in the nose often do not detect one single molecule but are detecting complex mixtures. And just because dogs can smell Covid in sweat samples doesn’t mean the pets can do so on a full human body, which offers a greater combination of aromas.


Cynthia Otto, director of the Penn Vet Working Dog Center at the University of Pennsylvania not involved in the study tells Science News, dogs that work well in that lab setting may not work well in a people setting. Handlers can also influence the dog’s response and must be able to read the dog well.



THE CONVERSATION: “Dogs can be trained to sniff out COVID-19 – a team of forensic researchers explains the science.”

SCIENCE NEWS: “Trained dogs sniff out COVID-19 as well as lab tests do.”