Dogs have millions more olfactory receptors in their noses than humans, giving them a salient talent for sniffing out threats ranging from illicit drugs and invasive pests to bombs and criminal suspects.

Now four dogs on Maui are joining an international effort to figure out whether canines can detect a distinct scent found in the sweat of people infected with the new coronavirus.

The hope is that dogs will one day be deployed in airports, schools and hospitals to swiftly screen crowds for people infected with COVID-19.

The research underway by The Queen’s Medical Center, which will tap into its network of patients to find participants, and Assistance Dogs of Hawaii will contribute to a pioneering study spearheaded by the London School of Hygiene and Tropical Medicine.

“The idea is to identify people who are positive with the virus in a noninvasive way,” said Dr. Whitney Limm, executive vice president of clinical integration at The Queen’s Health Systems. “It’s similar to using a dog to detect drugs and explosives and banknotes.”

Dogs have contributed to cutting edge medicine before. In fact, many human diseases have an odor that dogs can pick up on, including diabetes, malaria and certain types of cancer.

On the Big Island, a dog trained to sniff out the smell of rapid ohia death in the sapwood of ohia lehua trees before it becomes visible to humans aided recent efforts to thwart the fungal infection that has felled hundreds of thousands of trees across the state.

The ability to train dogs to reliably diagnose human COVID-19 infections could help slow the spread of the virus, especially in heavily trafficked public spaces.

Dogs already are being used in experimental trials at airports in Finland, Lebanon and the United Arab Emirates to identify COVID-19 in sweat wipes used by airline passengers exiting a flight. Preliminary findings in Finland suggest that dogs can be trained to detect the virus faster and more accurately than nasal swabs tested in laboratories.

But these experiments have not been peer reviewed.

Jonathan Jarry, a science communicator at McGill University who is not involved in the project, said the trials show promise as a proof of concept, but he doesn’t expect to see disease-sniffing dogs widely in the real world any time soon.

That’s because it would be hard to bring the concept to scale, considering that training dogs to sniff out disease is time intensive. And scientists don’t yet know exactly what molecule the dogs’ noses are picking up on when they identify a coronavirus sweat sample by scent, Jarry said.

There’s also a lot of variation in how well dogs of the same breed can correctly declare whether a person is positive or negative for the disease they were trained to detect.

That means that disease-sniffing dogs aren’t as reliable as society needs them to be if they are to be used as a stand-in for a more traditional diagnostic test, Jarry said.

“It’s difficult to manufacture COVID-sniffing dogs in a way that’s reliable, sustainable and scalable,” Jarry said. “I would argue that the future of pandemic testing lies in automated technologies for rapid testing where within 15 minutes you will know whether a sample is positive for COVID-19 or not — not dogs, as adorable as they are.”

Hawaii’s efforts to determine whether dogs can sniff out the virus will rely on sweat samples collected in a different way than the overseas trials.

Experiments Not Peer Reviewed

Volunteers who recently tested positive for the virus will agree to wear a face mask for three hours and a T-shirt and socks for 12 hours, then to turn these clothing items over to The Queen’s Medical Center. The garments will be flown to Maui, where they’ll be used to teach the scent of COVID-19 to three Labrador Retrievers and a Golden Retriever.

Sweat itself does not actually contain the virus, so the experiment is safe for the dogs, researchers and participants.

The dogs’ trainer is Maureen Maurer, executive director of Assistance Dogs of Hawaii, a nonprofit organization. She has a master’s degree in canine studies and led a 2016 study that used dogs to detect life-threatening bacterial infections in people.

The dogs — Sadie, Samson, Yuki and Tess — will be trained over a period of two to three months, first with sweat samples from people infected with the coronavirus.

Later phases of the study will use sweat samples from people who do not have the virus and will focus on teaching the dogs to differentiate positive and negative COVID-19 sweat samples.

The study, which begins this month, depends on the participation of about 100 adult volunteers on Oahu who have recently tested positive for COVID-19.