COVID-19 testing may be going to the dogs. As the prevalence of antigen testing for COVID-19 declines, scientists and dog trainers around the world are harnessing their powerful sense of smell to sniff out COVID-19 infections, including those in asymptomatic people.

According to The Wall Street Journal, with their more than 300 million scent receptors, dogs have been used to detect cancer, malaria, and diabetes. Professor Dominique Grandjean, from the National Veterinary School of Alfort, France says “this is the first time dogs have been trained to detect a viral disease in humans.” Grandjean says that dogs could check a large number of people in a short period of time, making the use of canine detection more efficient than nasal swabs.

According to Fast Company, dogs are well-known for their ability to sniff out many diseases. British researchers were awarded a contract last year to train bio-detection dogs as a rapid-testing measure for COVID-19. The U.K. government partnered with the Medical Detection Dogs charity and several universities to develop the program.

“When you have a disease, whether it’s a virus or a parasite, it changes the body odor, so you actually smell differently. We’ve demonstrated this already with diseases like malaria, for example,” Professor John Logan, head of London’s School of Hygiene and Tropical Medicine, told Euronews.

One dog can screen up to 300 people daily, says the World Health Organization. WHO is coordinating a global task force to further study the deployment of sniffer dogs to complement traditional diagnosis tools, says the Journal. Grandjean says that a PCR test costs $91.00, whereas a canine check is only $1.20.

He added that dogs can be trained to detect COVID-19 infections with 82% to 99% sensitivity and 84% to 98% specificity. Other studies have confirmed the high rate of accuracy in canine screenings. The Journal notes that these results are superior to rapid antigen tests that identify 72% of symptomatic people and 58% of asymptomatic people with COVID-19, according to a report published in Cochrane Library, a non-profit research group.

The dogs have already been used by the Miami Heat and other members of the National Basketball Association, Nascar, several airports worldwide, and private companies to detect COVID-19. Even hospitals are finding them useful for several reasons.

“It’s an extra layer of protection and it’s a lot more pleasant than having a swab stuck your nose,” said Robert Meade, CEO at Doctors Hospital in Sarasota, Florida. The hospital started using Buffy, a yellow Labrador Retriever, to sniff out visitors in April. If Buddy detects COVID-19, she sits by the person’s feet awaiting a treat. That individual must get a nasal swab before entering, says the Journal.

While the canines offer promise in preventing new infections and detecting the incidence of new variants of the coronavirus, they also offer emotional support by their presence.

Meade says that at the Doctors Hospital, Buffy has been a soothing presence for both staff and visitors. “It’s like pet therapy,” he said, according to the Journal, adding that he adopted Buffy to live with his family.