photo: a dog being trained to detect Covid-19
This very good boy is being trained to detect the odor associated with infection, an approach researchers believe can be used to screen Covid-19. London School of Hygiene and Tropical Medicine/Medical Detection Dogs

In the U.K., researchers believe they can train dogs to sniff out the distinctive odor of coronavirus, potentially assisting in mass infection screening efforts.

Researchers in the U.K. are working on an unusual weapon in the fight against Covid-19: dogs. Scientists at the London School of Hygiene and Tropical Medicine (LHTSM) believe that they can train dogs with a particularly keen sense of smell to diagnose people with the illness, even if they are displaying no symptoms. The project, which is currently undergoing crowdfunding, hopes to train and deploy dogs as screeners for people with Covid-19 in as little as two months. First, however, the team have to verify one key point: that the idea actually works.

There’s a good chance that it will. Dogs are already widely used to detect the presence of cancers, bacterial superbugs and neurological diseases such as Parkinson’s. Working with the charity Medical Detection Dogs, the LSHTM has previously carried out a successful training program that demonstrated dogs could detect malaria, creating a test that exceeded required World Health Organization standards.

“It’s very early stages,” says James Logan, head of LSHTM’s Department of Disease Control. “We know diseases have odors —  including respiratory diseases such as influenza — and that those odors are in fact quite distinct. There is a very, very good chance that Covid-19 has a specific odor, and if it does I am really confident that the dogs would be able to learn that smell and detect it.”

The actual source of the detectable scents created by diseases and viruses has not been determined, but Logan’s team believe they may be connected to the oxidative stress caused by infections.

“Oxidative stress can release compounds into the blood, which can be released through your breath and skin,” Logan says. “We think it may be something to do with the stress response to an infection that causes these different volatile chemicals to be produced, which are released into the blood and become detectable by the dogs. But we don’t know what the mechanism is.”

Not all dogs are suitable to be trained for this kind of diagnosis. LSHTM is working with just a few dogs — among them, a cocker spaniel and a Labrador retriever — who possess both an unusually acute sense of smell and the ability to be trained. Some already have experience with malaria screening. It may take a month to six weeks to train the animals to recognize the odor of samples from people with Covid-19, and to differentiate them from people with no infection or those with common colds. Once trained, even a small number of dogs could make a major difference.

“We have four or five dogs ready to go into training right now,” says Logan. “If we were able to deploy them within a month or two, we could screen maybe 4,000 to 5,000 people per day. In the short-term, there are some locations where dogs might be appropriate to us such as screening medical or care staff, or people going into schools and other community areas.”

In the absence of mass testing and tracing of cases, virus-sniffing dogs could also be deployed in airports, train stations, and transit hubs, to screen unwitting Covid-19 carriers before they accidentally spread the infection in crowded urban spaces. All this, of course, depends on the project proving successful in isolating the odor. But a future in which coronavirus is far easier to detect, manage and isolate — thanks to one of humankind’s oldest and most steadfast friends — offers a more hopeful vision of the pandemic’s resolution.

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