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Are dogs really that good at sniffing out COVID? Another study leaves no doubt

Dogs’ noses have about 300 million scent receptors.
One Betta is one of four dogs being trained to sniff out COVID-19 at Florida International University. (

We don’t yet know what concerts, festivals and other large gatherings will look like after the COVID-19 pandemic is under control, but you may want to start adding dogs to the picture.

Canine presence is already normal at airports where dogs search for weapons, explosives, drugs or other dangerous materials. But they have been gradually making appearances at large events to sniff out COVID-19 following research that revealed their powerful noses could detect if a person was carrying the virus.

They’ve perused Miami Heat basketball games, scanned NASCAR races and inspected nursing home residents.

But just how accurate are they? A new “proof-of-concept investigation” by researchers at the University of Pennsylvania adds more evidence to the pile.

In its study, nine dogs were able to identify positive coronavirus samples with 96 percent accuracy on average after three weeks of training.

Researchers say using dogs can help catch people who are infected and don’t know it — otherwise known as asymptomatic carriers — before they spread the virus to others. This method is also cheaper than traditional testing practices. The study was published Wednesday in the journal PLOS ONE.“This is not a simple thing we’re asking the dogs to do,” Cynthia Otto, senior author of the study and director of the University of Pennsylvania School of Veterinary Medicine Working Dog Center, said in a statement. “Dogs have to be specific about detecting the odor of the infection, but they also have to generalize across the background odors of different people: men and women, adults and children, people of different ethnicities and geographies.”

The team trained eight Labrador retrievers and one Belgian Malinois to identify whether urine or saliva samples from hospitalized adults and children were COVID-19 positive. All samples were “inactivated” to prevent the dogs from getting infected.

A “scent wheel” with 12 ports containing coronavirus positive and negative samples, as well as some controls such as gloves, paperclips, empty cans and garlic on filter paper, was presented to the dogs. If they responded to a COVID-19 positive sample, the dogs were rewarded.

Although the canines detected positive samples with high accuracy, their ability to avoid false negatives was lower, likely because of the strict study criteria, the researchers said. “If the dogs walked by a port containing a positive sample even once without responding, that was labeled a ‘miss.’”

There was one sample that kept calling the dogs’ attention, however. The patient it came from tested negative for COVID-19, but they had recently recovered from the disease.

“The dogs kept responding to that sample, and we kept telling them no,” Otto said. “But obviously there was still something in the patient’s sample that the dogs were keying in on.”

Dogs’ noses are good at their jobs

Dogs’ noses, with about 300 million scent receptors, are exceptionally good at their jobs. In comparison, humans only have about 5 or 6 million, according to the American Lung Association, which says “a dog can even detect a teaspoon of sugar diluted in a million gallons of water (the equivalent of two Olympic sized pools).”

Dogs have been trained and deployed to detect illnesses, too, including lung cancer, diabetes and Parkinson’s disease, to name a few. Experts believe sick people emit specific chemicals that create a scent dogs can pick up on.

The UPenn study isn’t the first to test if canines are capable of sniffing out COVID-19.

A study out of Germany trained eight dogs for a week using scent holes with hidden metal containers filled with nose and throat samples from COVID-19 infected or non-infected patients. The dogs were able to correctly identify 94 percent of the 1,012 patient samples.

Another project in Paris presented eight dogs with 198 sweat samples, half of which were COVID-19 positive. When hidden in a row of negative samples, the dogs detected the positive ones 83 to 100 percent of the time.
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