Dogs can detect Covid with high accuracy, even asymptomatic

 Questions about whether dogs can sniff out Covid — and how well — have intrigued researchers since early in the pandemic.

A study published Wednesday in the journal Plos One offers further evidence that dogs can indeed be trained to detect Covid. The dogs tested in the research accurately identified 97 percent of positive cases after sniffing human sweat samples. That made them more sensitive than some rapid antigen tests.

The samples were collected at community centers in Paris from a mix of symptomatic and asymptomatic cases, as well as healthy people without Covid. The researchers found the dogs to be especially good at detecting asymptomatic infections, with a sensitivity nearing 100 percent.

Previous studies have also highlighted this canine skill: Researchers in Florida last year found that that dogs could predict positive Covid tests with 73 to 93 percent accuracy after a month of training. In a U.K. study, dogs accurately pinpointed 82 to 94 percent of positive cases.

The new study was conducted in early 2021, so the dogs were identifying the original coronavirus. Dominique Grandjean, one of the study’s authors and a professor at the Alfort National Veterinary School in France, said he’s now examining how well dogs pick up on variants.

Grandjean said his findings suggest that dogs might be useful for detecting Covid in airports, nursing homes, schools, or sporting events. Already, dogs have helped sniff out Covid at airports in Saudi Arabia, Finland and the United Arab Emirates.

Dogs "only need a few molecules" to identify a positive case, Grandjean said.

But Dr. Cynthia Otto, director of the Penn Vet Working Dog Center at the University of Pennsylvania, said it's difficult to train dogs to detect Covid in the real world.

"The ideal — and I would consider it the Holy Grail — is that the dog is just standing there, a person walks by, and they say, 'Yes, no, yes, no, yes, no,'" Otto said. "That eventually could be done, but making sure it’s done with all the proper controls and quality assurances and safety — it’s a big step. I haven’t seen anyone who has proposed how to make that transition in a way that’s scientific and safe."

A less invasive way to detect Covid?

For the new study, researchers trained five dogs by rewarding them with toys for detecting a positive Covid sample.

The dogs then sniffed 335 sweat samples, 109 of which were positive on PCR lab tests. Each sample was placed in a tiny box behind a cone, with the cones lined up in rows of 10. If a dog thought it detected a positive case, it would sit down.

Grandjean estimated that it took just 15 seconds for the dogs to analyze 20 Covid samples. When it came to categorizing negative samples — known as specificity in testing — the dogs were slightly less accurate. They identified 91 percent of the Covid-free samples correctly, meaning they gave some false positives.

Still, Grandjean said, dogs offer a couple advantages for Covid testing: They’re less invasive than a nasal or throat swab and provide more immediate results (not counting the training time).

https://www.nbcnews.com/health/health-news/dogs-detect-covid-accuracy-rcna31438