Dogs can detect Covid-19 faster, more precisely and cheaper than the best technology out there, according to a new study. Researchers did a meta-analysis of studies published over the last two years and found they all highlighted the power of dogs in detecting the virus and its variants, even when it is obscured by other viruses.

While humans generally experience the world through sight, dogs use scent to learn about the environment that surrounds them. Their noses are crucial for finding food, mates and safe spaces. Dogs’ sense of smell is up to 10,000 times better than ours, thanks to having a proportionately larger nose with over 100 million scent receptors.

Tommy Dickey from UC Santa Barbara and Heather Junqueira from BioScent, a company that trains medical detection dogs, compiled a review of 29 peer-reviewed studies that indicate a consensus among researchers over dogs’ skills in detecting Covid-19. The studies covered 400 scientists, 30 countries and 31,000 samples.

From the studies, Dickey and Junqueira agree that trained scent dogs are “as effective and often more effective” than antigen tests people use at home, as well as PCR tests used 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 creating any plastic waste.

“They’re much more effective. In fact, one of the authors that we quote in the paper commented that the RT-PCR test is not the gold standard anymore. It’s the dog,” Dickey said in a news release. “And they’re so quick. They can give you the yes or no within seconds, if they’re directly smelling you.”

Dogs have the ability to identify Covid-19 in individuals who are in the pre-symptomatic or asymptomatic stages, even when their viral load is not high enough for standard tests to yield accurate results. Furthermore, they can also distinguish between Covid-19 and its variants when confronted with other respiratory viruses.

In some studies, the dog gave the person a quick sniff and sat down to indicate the presence of Covid-19. In others, the dog was given a sweat sample to smell, a process that can take a few minutes. Scent dogs, such as beagles, would be the ideal dog, the researchers said, due to their natural tendency to rely on odors to relate to the world.

A fantastic nose

The magic lies in their noses, the researchers said. Dogs have hundreds of millions of olfactory receptors and a third of their brains are used for interpreting smells — compared to 5% in humans. This allows them to detect smells at much lower concentrations than humans, sometimes as low as one part per trillion.

Dogs have previously shown they can identify many infectious diseases via scent, as Jacqueline Boyd, a UK researcher, explains in The Conversation. For example, kids infected with malaria were identified by dogs smelling their foot odor. Dogs can also detect urinary tract and gastrointestinal infections caused by life-threatening bacteria.

However, the researchers agree there are still challenges to placing dogs in the mainstream of medical diagnoses. “There’s quite a bit of research, but it’s still considered by many as a kind of a curiosity,” said Dickey. Colombia and Finland are some of the few countries that have used dogs in field experiments, he added.

“Scent dogs deserve their place as a serious diagnostic methodology that could be particularly useful during future pandemics, potentially as part of rapid routine health screenings in public spaces,” the researchers wrote in a news release. “Medical scent dogs are finally ready for a host of mainstream medical applications.”

The study was published in the Journal of Osteopathic Medicine.