These COVID-Sniffing Canines Are on the Job at Nursing Homes in Marin County

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A dog wearing a vest and collar sniffs a hand of a person wearing a medical uniform, blue pants, a red pack on their waist and white shoes holding a leash.
Early Alert Canines sniffing dog Scarlett patiently awaits instructions from her handler. (Courtesy of Marin County Health and Human Services)

Dogs are detecting COVID in long-term care facilities in California, with an accuracy almost on par with rapid tests. Currently, two white labradors named Scarlett and Rizzo are on the job in Marin County.

In less than a half hour, dogs can scan hundreds of patients at a nursing home by sniffing their shoes and ankles. If they identify COVID, they will sit down next to the suspected resident. A rapid antigen test can verify the results.

The canines are sniffing for unique volatile organic compounds (VOCs) released in human breath or sweat when someone is positive for COVID. Dogs have hundreds of millions more specialized odor-detecting neurons than humans, which means a dog can detect the equivalent of one drop of a liquid in 20 Olympic-sized swimming pools.

“Think about what we use dogs for,” said Dr. Carol Glaser, medical officer for California’s infectious disease labs. “We use them to sniff bombs. We use them for drugs. They can search for dead bodies under thousands of tons of rubble. It's not surprising that they would be able to do this.”

An elderly person wearing a black top and blue jeans sits in a wheelchair while a person dressed in a hospital uniform stands over a person in bed with a dog beside them.
Long-term care facility residents are receiving support from Bay Area nonprofit Early Alert Canines sniffing dogs trained to detect COVID. (Courtesy of Marin County Health and Human Services)

In COVID field trials, Scarlett and Rizzo are right about 80% of the time, compared to antigen tests at 81%–91%.

“We think that they can get better,” said Glaser. “We know in the controlled lab setting, when they were using what's called the scent wheel, they were over 95% very consistently. So, we know we can get there.”

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The scent wheel is like a multiple-choice test with various odors. The device is a training tool that can desensitize dogs to non-target odors they may encounter during searches. During eight weeks of initial training, Scarlett and Rizzo correctly identified the socks of COVID-positive patients nearly all the time.

During the fall of 2021, the dogs sniffed for COVID at schools around San Francisco. They screened students before and after proms, and the canines were helpful in special needs classrooms where students often struggled to self-swab. Similar efforts have unfolded in Florida, Hawaii and Massachusetts.

Researchers across the world are training dogs to detect COVID. A team in France and scientists in the United Arab Emirates worked with dogs who identified COVID in sweat samples collected from people’s armpits. In Finland, four dogs were trained to detect COVID at the airport using skin samples collected from various body parts.

Two dogs wearing collars attached to leashes in a hallway with one sitting on the right and the other standing to the left.
White labs Scarlett and Rizzo have been trained by Bay Area nonprofit Early Alert Canines in a laboratory setting to detect odors specific to COVID-19. (Courtesy of Marin County Health and Human Services)

Currently, dogs are trained to monitor patients with diabetes. If a patient’s blood sugar drops or spikes, canines alert owners with a paw or a nudge to head off a medical emergency. However, as this NPR investigation highlighted, “The diabetic alert dog industry is unstandardized and largely unregulated. And the science on a dog's ability to reliably sniff out blood sugar changes is, at best, inconclusive.”

As with COVID sniffers, more research is needed before people can fully depend on dogs.

However, Glaser hopes canines can eventually sniff for influenza or norovirus at nursing homes.  She says sweeping a facility with dogs is much cheaper than traditional testing, requires fewer staff and eliminates the majority of plastic waste.

“You know it may be that this has been under our noses, so to speak, and we haven’t even recognized it,” said Dr. Matt Willis, public health officer for Marin County.

Two people wearing face masks, medical gear and gloves stand in front of a mobile maintenance table with medical supplies on top.
Medical workers check confirmatory COVID tests to ensure the pilot program data reflects accurate results. (Courtesy of Marin County Health and Human Services)

He says the bias toward tech solutions prevented people from tapping canines earlier in the pandemic. Willis envisions a day when all public health departments train canine units just like the police.

“We could imagine dogs moving from facility to facility or school to school, and just screening everyone in a matter of minutes,” said Willis.

Sometimes Scarlett and Rizzo — the COVID dogs — can detect the virus a day or two earlier than a traditional test will register as positive. But overall, the canines are still not quite as sensitive as lab tests. As soon as they are, the state plans to scale canine diagnostics for COVID across California.