Dogs Detect Positive Covid Infections Better Than Antigen Tests, Study Suggests


Dogs were more effective at detecting positive cases of Covid-19 through human sweat samples than nasal antigen tests, a PLOS ONE study conducted by researchers affiliated with the Assistance Publique-Hôpitaux de Paris found, suggesting a potentially less invasive and quicker Covid testing alternative.

A dog correctly detects a sample of malaria.

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Key Facts

In the study, dogs were 97% effective at detecting a positive case of Covid compared to PCR tests—the most accurate Covid test—while nasal antigen tests detected 84% of positive Covid infections.

The study—which included PCR and sweat samples from 335 people and antigen tests from 234 people recruited from two community Covid testing centers in Paris from March 16 and April 9 2021—found canines were 100% accurate in detecting positive Covid cases in asymptomatic individuals compared to PCR test results.

Canines were slightly less effective at identifying negative coronavirus infections, detecting 90% of negative cases compared to antigen tests that were 97% accurate.


To carry out the study, researchers created 10 stations with human sweat swabs placed behind cones so canines would avoid direct contact with potentially infectious samples. Each cone was sniffed by at least two dogs, which indicated a test was positive by touching their mouth to the side of the cone, according to photos from the study.

Surprising Fact

It can take only three weeks for a dog that is already trained in odor detection to learn how to detect the coronavirus. For “green dogs,” or dogs who have yet to be trained, it can take around five to six weeks, as the canines also have to learn marking methods, according to the researchers. Researchers trained the dogs by using toys as a positive reinforcement tool, according to the study.

Big Number

Up to 300 million. That’s how many olfactory receptors dogs have in their noses, compared to roughly six million in humans, giving dogs a sense of smell potentially 10,000 times stronger than humans.

Key Background

Several preliminary studies using sweat samples from hospitalized patients have shown dogs can be efficient in detecting cases of the coronavirus, but this study is one of the first to compare dog detection abilities to antigen tests, according to researchers. Dogs could offer a more immediate and less invasive Covid testing method compared to PCR tests, which are taken through a nasal or saliva swab and can take several days to complete. Research has also suggested dogs may be capable of detecting a variety of other illnesses in humans, including breast and ovarian cancer and diabetes. Researchers suggested future studies should focus on direct sniffing by dogs to conduct mass testing in crowded spaces like airports and train stations, though such an approach could potentially expose dogs to Covid and cause problems for humans who are fearful of dogs, researchers noted.

Further Reading

Diseases that dogs can detect (Guardian)

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