Dogs may be able to sniff out COVID-19 infections, early research suggests

ByVirginia Langmaid, CNN, CNNWire
Tuesday, May 25, 2021
Dogs may be able to sniff out COVID infections, research suggests
A new study of six dogs shows they were all able to pick up the distinctive odor of COVID produced by those with the virus, after six weeks of training.

A new study published Sunday indicates dogs might be able to lend a helping paw in the fight against COVID-19.

In a collaboration between the London School of Hygiene & Tropical Medicine, Durham University and the group Medical Detection Dogs, scientists completed Phase 1 of a trial examining whether, under controlled conditions, dogs might be able to smell and identify COVID-19 infection.

Six dogs participated in the study, ranging in ages from 4 to 6 years old. The group included Labrador, Golden Retriever and Cocker Spaniel breeds. Researchers said the dogs were able to pick up the scent of COVID-19 after six to eight weeks of training.

The early results have been published in a preprint study -- meaning the work has not yet been peer reviewed or published in a medical journal.

In the Phase 1 trial, working dogs were tasked with detecting COVID-19 on samples of clothing and masks. Researchers examined whether the dogs could distinguish between samples positive and negative for COVID-19.

"The results are extremely exciting," said James Logan, a project lead on the study.

The dogs showed a sensitivity rate of around 82%-94% in detecting COVID-19. Chemical analysis of the infection showed a "distinct" odor associated with COVID-19. Researchers are in the process of identifying the exact chemicals behind this odor.

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Dogs will sniff fans before they enter by walking past them. If the dog sits, that signals they may have detected COVID-19.

"Dogs could detect COVID with incredible speed and accuracy," Logan said -- "even if a person was asymptomatic."

The specificity rate, which measured the ability of the dogs to indicate whether someone did not have COVID-19, ranged from around 76% to 92%.

Study authors say a PCR test is still the "gold standard" for detecting COVID-19, but suggest dogs could provide a quicker and easier way to screen for COVID-19 in high-volume traffic areas. The dogs could also dissuade people from going to high-contact spaces while infected.

"The other thing about dogs is that they would serve as a visual deterrent, so if people knew that dogs were going to be screening at the airport, it's very likely that people would think twice about traveling if they were infected," Logan said.

Still more work to be done

While early results appear promising, it is likely too early to know whether COVID-sniffing dogs could actually be used as a tool to fight the pandemic in the real world.

"This could be compromised by the density of individuals in crowded spaces and whether well-ventilated external spaces, where odours are rapidly dispersed, compromise the ability of the dogs to detect individuals with low levels of infection," Lawrence Young, a virologist at Warwick Medical School who did not contribute to the study, said in a statement.

Young said the research was "not to be sniffed at," but that more work is needed.

"The big question is will this approach work in the real world on people rather than samples of socks and shirts?" he said. "There is variation from dog-to-dog particularly in specificity which could result in increased numbers of false positives."

COVID-19 infection and dogs

COVID-19 can infect dogs, which could make these kinds of programs risky for the working dogs themselves, Mick Bailey, a professor of comparative immunology at the University of Bristol's Veterinary School, who was unaffiliated with the research, said in a statement.

"Infection of dogs with SARS-CoV-2 has been reported, both asymptomatic and associated with variable levels of disease as in humans, so using dogs deliberately to sniff breath and clothes from potentially infected people seems a bit of a risk to the dogs, let alone their handlers," he said.

SARS-CoV-2 is the name of the virus that causes COVID-19.

"You'd need to have some way round that, like vaccinating the sniffer dogs. Currently, no SARS-CoV-2 vaccine is licensed for use in dogs although there's no reason to think that the ones approved for humans wouldn't work, but the low reported incidence of infections in dogs would make a phase 3 trial difficult," Bailey said.

Both unaffiliated experts confirmed to CNN that dogs have been shown to sniff out infections in general, and previous studies have suggested they can indeed detect COVID-19 infection. However, the specificity of the detection is a looming question, Bailey said.

"It could be, for example, that the signature that the dogs are detecting might be a general one associated with respiratory viruses like influenza, rather than a specific one associated with SARS-CoV-2," he said.

Phase 2 of this study will involve testing the dogs' detection abilities on people actually infected with COVID-19, not just samples of clothing.

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