Dogs have already been trained to smell drugs, cancer, and even blood sugar changes in people with diabetes. Now they're learning how to smell Covid-19. In trials, dogs detected the virus over 95% of the time, more accurately than rapid blood or swab tests. The dogs have even been able to detect Covid in people who aren't showing symptoms yet, which taking temperatures can't do.
Several countries around the world are working to develop these skills in dogs. To train them, sweat from people with Covid is collected and put on cottonballs. After they've learned to identify the scent, they then have to choose the cottonball with the sweat on it from lots of untreated cottonballs.
Even though the dogs are expensive, it actually costs less to train and use dogs for Covid detection than for other types of rapid testing. And one dog can cover a lot of space at once, effectively testing hundreds of people in a few minutes. More training and research is needed before the dogs will be used widely, but many hope that very soon dogs will be able to sniff around at airports and sports stadiums and other crowded places to catch Covid before it spreads.
Dogs have about 300 million receptors for smell in their noses, compared to 6 million in humans. So it's relatively easy for them to smell the particular chemical compounds a person with Covid produces in their sweat. The accuracy is still debated, but in real-life trials it's been good. They're not only useful in crowded spaces, but also for detection in remote areas where people can't get to testing sites, or for housebound folks.