Governments and households around the world spent fortunes during the COVID-19 pandemic on equipment to detect an infection. Yet scientists in California who have conducted a meta-analysis of more than two-dozen studies showed there was an easier way: A dog’s nose knows.
It’s an idea that has finally gained scientific consensus: As any dog owner will quickly discover, canines have up to 300 million olfactory receptors in their noses, compared with about six million in humans. The part of a dog’s brain that is devoted to analyzing smells is about 40 times greater than ours.
The meta-analysis found that dogs’ sense of smell can be a faster, more precise, less expensive – not to mention friendlier – method for detecting COVID-19 than even our best current technology. A growing number of studies over the last two or so years has highlighted the power of dogs in detecting the stealthy virus and its variants, even when they are obscured by other viruses, such as those from common colds and flu. All these enhancements mean that dogs can detect very low concentrations of odors associated with COVID infections.
“They can detect the equivalent of one drop of an odorous substance in 10.5 Olympic-sized swimming pools.”
Tommy Dickey
“They can detect the equivalent of one drop of an odorous substance in 10.5 Olympic-sized swimming pools,” University of California at Santa Barbara Prof. Emeritus Tommy Dickey said. “For perspective, this is about three orders of magnitude better than with scientific instrumentation.”
In some cases, dogs were able to detect COVID in presymptomatic and asymptomatic patients whose viral load was too low for conventional tests to work.
“It went from four papers to 29 peer-reviewed studies – that includes more than 400 scientists from over 30 countries and 31,000 samples,” said University of California at Santa Barbara Prof. Emeritus Tommy Dickey, who analyzed the massive number of studies together with collaborator Heather Junqueira of BioScent, Inc.
Their meta-analysis was published in the Journal of Osteopathic Medicine under the title “COVID-19 scent dog research highlights and synthesis during the pandemic of December 2019 to April 2023.”
How can dogs sniff out COVID-19?
From their rigorous survey of peer-reviewed studies published by traditional academic publishers covering both field and clinical experiments, Dickey and Junqueira said the collective research demonstrated that trained scent dogs were “as effective and often more effective” than the antigen tests we’re keeping handy at home, as well as the gold-standard reverse transcription polymerase chain reaction (RT-PCR) tests deployed in clinics and hospitals. Not only can dogs detect the SARS-CoV-2 virus faster, they can do so in a non-intrusive manner, without the environmental impact that comes with single-use plastics.”
“They’re much more effective,” Dickey said.
“In fact, one of the authors that we quote in the paper commented that the RT-PCR test is not the gold standard anymore,” he added. “It’s the dog, and they’re so quick. They can give you the yes or no within seconds if they’re directly smelling you.”
In some scenarios, the dog gave the person a quick sniff, sitting down to indicate the presence of COVID. In others, the dog was given a sweat sample to smell, taking just a few minutes. The speed is especially important in situations like the earlier phase of the pandemic, when a gap of days between test and result could mean an exponential rise in infections if the person was positive, or scenarios that involve a high volume of people.
Scent dogs, such as beagles, basset hounds, and coonhounds, would be the ideal canines for the task, given their natural tendencies to rely on odors to relate to the world. But the studies showed a variety of other dogs are up to the challenge. Given a few weeks of training, puppies and older dogs, males and females, and purebreds and mixed breeds all performed admirably. In one study, a “problem” pit bull terrier that had been abused found a second chance by becoming a perfectly capable COVID detector.
Despite these glowing reviews, there remain challenges to placing man’s best friend in the mainstream of medical diagnoses, although the animals have proven successful in the detection of other conditions, such as diabetes and cancer.
“There’s quite a bit of research, but it’s still considered by many as a kind of a curiosity,” said Dickey, whose love for Great Pyrenees dogs led him to become a certified therapy dog handler and author of therapy dog books after he retired from teaching.
Places that were open to using dogs in field experiments tended to be smaller countries, such as Finland and Colombia, where there was a desire to explore fast and cost-effective methods of detecting COVID without having to wait for expensive tests to be developed or for reagents to become available.