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With up to 300 million scent receptors, dogs are among the  in the animal world. The human nose, by comparison, contains only around 6 million scent receptors. Dog brains also devote  than humans to analyzing odors.

That’s why people train dogs to search for diverse targets via smell, from  and  to ,  and more. Dogs accomplish this by successfully recognizing the odors of substances called  that are specifically associated with these targets. Not only can trained dogs detect these volatile organic compounds, but oftentimes they can do it with  analytical instruments.

Volatile organic compounds can be produced by living organisms as well as by natural or synthetic materials. In humans, they are produced by the body’s metabolic activity, then enter the bloodstream and are finally released into the air through blood, urine, feces, skin or breath.

Scientists have found that dogs can be trained to successfully recognize unique volatile organic compounds, called “biomarkers,” in the  with certain diseases or chronic medical conditions, including  and , as well as for  in epileptic individuals.

Our team of canine scent scientists at Florida International University wanted to figure out whether COVID-19 is among the diseases that trained dogs can detect. , which we carried out with our colleague, , confirms that it is.

We believe that dogs hold great promise as a rapid screening method that, used with other measures , can help stop COVID-19 spread and end the pandemic. Some of the dogs trained during our research have already proved their abilities  and public events.

Training dogs to detect COVID-19

For several decades, Florida International University’s  has been a global institution for . The majority of this research has focused on identifying the specific volatile organic compounds that natural or synthetic materials and living organisms produce and which dogs can be trained to detect.

In , we hypothesized that people infected with COVID-19 would release specific volatile organic compounds, and that a well-trained odor detection dog would be able to tell these biomarkers apart from other volatile organic compounds.

So in collaboration with Baptist Health South Florida, a nonprofit health care organization, we obtained face masks from hospitalized patients with confirmed COVID-19 diagnoses, as well as from those who tested negative for COVID-19.

We then trained four dogs to respond to COVID-19 positive masks, while ignoring COVID-19 negative masks and unused masks. In the process, the dogs learned to tell the difference between biomarkers originating from COVID-19 breath and from non-COVID-19 breath.

One of the training tools we used was a scent detection wheel. We placed both COVID-19 positive and COVID-19 negative masks in cans with small holes in the lids, which were attached to the ends of the wheel’s arms. The dogs then walked around the wheel sniffing the volatile organic compounds coming out of these holes.

After 40 double-blind trials – meaning that the people training the dogs didn’t know which masks were which –  each of the four dogs in this study accurately detected COVID-19 positive masks more than 90% of the time.

Mac, a Terrier mix, got it right in 96.2% of attempts. Cobra, a Belgian Malinois, was correct 99.4% of the time. One Betta, a Dutch Shepherd, got it right in 98.1% of attempts, and Hubble, a Border Collie mix, 96.3% of the time.

After the study, Cobra and One Betta went to work at , in Tallahassee, Florida, screening for COVID-19 on surfaces. In May 2021, both dogs also put their COVID-19 detection skills to work  in Miami.

In September 2021, Cobra and One Betta worked for two separate  at Miami International Airport, screening individuals for COVID-19.

Other agencies are beginning to adopt FIU’s methods for training dogs to detect COVID-19. Recently, with FIU’s assistance, the Bristol County Sheriff’s Office in Massachusetts  named Duke and Huntah to work detecting COVID-19. These two dogs are  at facilities in the nearby Freetown-Lakeville Regional School District.

Next steps in COVID-19 detection

Now that we know dogs can be trained to sniff out COVID-19, our team hopes to identify the exact volatile organic compounds – the biomarkers – that they’re detecting. To accomplish this, we are continuing to analyze both COVID-19 positive masks and COVID-19 negative masks in the laboratory.

Pinning down which biomarkers are linked to COVID-19 will help in developing materials and training aids for teaching other dogs how to detect the disease.

It may also contribute to developing COVID-19 sensors for use in odor-detecting devices – which might then join rapid testing and sniffer dogs like One Betta, Hubble, Mac and Cobra in helping get the pandemic under control.