Their skills are developed in Thailand, the United States, France, Great Britain, Chile, Australia, Belgium and Germany, among other countries. They patrolled the airports of Finland, Lebanon and the United Arab Emirates, and private companies have used them at American sporting events.

Angel, a pale blonde with budding jowls and a penchant for crunchy plastic bottles, is the star of the pack at Chulalongkorn University. But as a group, the dogs trained in Thailand – Angel, Bobby, Bravo and three others, Apollo, Tiger and Nasa – accurately detected the virus 96.2% of the time in controlled environments, according to university researchers. Studies in Germany and the United Arab Emirates had inferior but still impressive results.

Thai Labradors are part of a research project jointly conducted by Chulalongkorn University and Chevron. The oil company had previously used dogs to test its offshore workers for illegal drug use, and a Thai official wondered if animals could do the same with the coronavirus. A dog’s ability to sniff out COVID-19 is, in theory, no different from his prowess at detecting narcotics, explosives, or a Scooby snack hidden in a pocket.

An “ideal detector”

The six dogs are assigned six handlers, who exposed them to sweat-stained cotton balls from the socks and armpits of HIV-positive individuals. Researchers say the risks to dogs are low: the coronavirus is not known to be easily transmitted through sweat, a commodity plentiful in tropical Thailand. Instead, the main route of transmission appears to be respiratory droplets.

On rare occasions, companion cats and dogs in close contact with infected humans have tested positive for the virus, as have populations of mink and other mammals. However, there are no proven cases of pets transmitting the virus to humans.

Within months of training, at around 600 sniffs a day, the Thai dogs sat obediently whenever they smelled the COVID-19 cell byproducts on cotton balls, which the researchers placed at nose height on a machine similar to a carousel.

Dogs, whose wet muzzle has up to 300 million olfactory receptors compared to about six million for humans, can be trained to memorize about 10 odor patterns for a specific compound. Dogs can also smell through another organ tucked between their nose and mouth.

Some research has suggested that dogs of different breeds may be able to detect diabetes, Parkinson’s disease, malaria, and certain cancers – that is, volatile organic compounds or body fluids associated with them.

Labradors are among the smartest breeds, said Lertchai Chaumrattanakul, who runs the Chevron part of the dog project. They are also affable, which makes them the perfect dog detector: engaged and greedy.

Questions remain

For a few hours in the morning and afternoon, the waste pickers take turns to survey a room furnished with metal arms that hang samples of sweat. By the way, they sniff up to 10 times per second, as dogs are used to. (Humans tend to only handle one inhalation every second or so.)

Then they retire to their living quarters for a nap and the occasional belly massage.

“Their lives are good, better than those of many humans,” said Thawatchai Promchot, manager of Angel, who worked as a supplier to Chevron before turning to animal health screening.

Bangkok-based dogs are now testing sweat samples from Thais who cannot easily reach COVID testing sites, such as the elderly or bedridden. Dog wardens are working to set up a program with the city’s prisons, where thousands of inmates have been diagnosed with COVID.

Cynthia Otto, director of the Penn Vet Working Dog Center at the University of Pennsylvania School of Veterinary Medicine, said she was concerned that until there was better research on the quality of dogs to detect the COVID in real situations, the method could allow people who are positive to go through undetected.

“I don’t want to miss them,” she said, “so everyone thinks they’re safe.”

There are still a lot of questions about using dogs to detect the virus.

What is the smell of vaccinated people? How easy will it be to train a large pack of COVID sniffer dogs around the world? What if people tested by a canine nose didn’t sweat so much? What if a dog contracts COVID and loses its sense of smell?

Still, Lertchai said he believes virus detection dogs will be a boon, especially in countries that don’t have the resources for more expensive tests.

“COVID is not going to go away, and there will be new variants,” he said.

“Dogs want to be helpful, so let’s use them. “

Hannah Beech written for the New York Times. These stories are part of the Solutions Journalism Network, a nonprofit organization dedicated to rigorous reporting on responses to social issues.