Dogs Can Sometimes Detect COVID-19 Better Than PCR Tests

Trained scent dogs might be able to detect COVID-19 just as accurately as—or even better than—PCR tests, according to a new review published in the Journal of Osteopathic Medicine.

Researchers compared the results of 29 peer-reviewed studies in which scent dogs were used to detect over 30,000 samples to those of PCR and rapid COVID-19 tests. The trained dogs were able to identify asymptomatic COVID-19 cases, people who had long COVID, and sometimes even new variants.

Tommy Dickey, PhD, MS, MA, a co-author of the review, said that the accuracy of the trained scent dog method is in some cases superior to standard COVID-19 tests “with much less environment impact.”

“Our review has shown that it is safe to utilize scent dogs to directly screen and test individuals who may be infected with COVID-19,” Dickey told Verywell.

How Can Dogs Detect COVID-19?

Among the studies that were reviewed, 23 were done in controlled clinical or laboratory settings, while six were conducted in public settings such as the Helsinki Airport, a metro system in Colombia, concerts in Germany, and a K-12 school in California, according to Dickey.

Some studies used samples (mostly breath, saliva) taken from individuals, while some used direct sniffing of individuals by the dogs. Either PCR or antigen tests were used for verification.

Labrador Retrievers and Belgian Shepherds were by far the most frequently utilized dog breeds, and they were often used in scent detection work for other purposes before the pandemic. Beagles were also good at detecting COVID-19 as well.

COVID-detection dogs were also faster than regular testing, giving results from only a few seconds to no more than 15 minutes.

“In several instances, it turned out that the standard tests were in error, and the dogs had correctly identified COVID positive individuals,” Dickey said.

Previous studies have also shown scent dogs’ ability to detect some cancers, diabetes, epilepsy, and Parkinson’s disease.

Dogs have an amazing sense of smell that can detect levels of chemicals far lower than the best sensors humans have been able to develop, according to Brian Labus, PhD, MPH, REHS, an expert in infectious diseases and an assistant professor of epidemiology and biostatistics at the UNLV School of Public Health.

They can smell COVID, or other infectious agents, just like they can explosives or drugs, Labus said. As long as the organisms have molecules that are unique, dogs could potentially be trained to detect any number of pathogens.

Why Aren’t We Using More Scent Dogs for Medical Diagnostics?

“This review makes the case that scent dogs could potentially be used to detect COVID or other pathogens,” Labus said. “Whether it is practical to do so is a completely different matter.”

Like humans, COVID-sniffing dogs can have “off-days” too, according to the study researchers. Some patients may also have allergies or feel uncomfortable with dogs. The screening process also requires a close relationship between a handler and a properly trained dog.

“There are a lot of practical challenges to using scent dogs as well, and those will have to be addressed before they can be seriously considered for large-scale population screening,” Labus said. “And by the time these challenges can be overcome, COVID may be a less common disease, which completely changes the economics of it.”

So while this review shows that there may be some merit to the approach to detect COVID, Labus said we still have a long way to go before we change our testing approach.

“For now, we will still be sending our COVID tests to the lab, not the Labrador,” he said.