If a study published yesterday is correct, public health officials and borders agencies could soon have a new weapon in the battle against Covid-19 – one with four paws and a wet nose

Dogs? Really?

Really. Researchers at the London School of Hygiene and Tropical Medicine, collaborating with charity Medical Detection Dogs (MDD) and the University of Durham, have found that dogs can be trained to detect a particular smell which is given off by people with Covid-19. They discovered that in trials with articles of clothing and used masks some of the dogs used could detect up to 94 out of every 100 infected people. That compares with between 60% and 80% accuracy for lateral flow tests and around 92% accuracy for polymerase chain reaction (PCR) tests.

That’s amazing

It is, but then dogs are – particularly when it comes to those wet noses. Dogs are able to dissolve odour particles from the air and then process the information in the 300 million or so olfactory receptors those noses contain. By way of comparison, the human nose contains about five million olfactory receptors, so the most accurate two-legged sniffer is way behind even a poor four-legged one. It’s why dogs have long been used to detect everything from drugs and explosives to tumours and incipient diabetes. “These fantastic results are further evidence that dogs are one of the most reliable biosensors for detecting the odour of human disease,” says Dr Claire Guest, Chief Scientific Officer at MDD. “Our robust study shows the huge potential for dogs to help in the fight against Covid-19.”

Are some dogs better than others?

Yes. The so-called gun dog breeds such as Labrador Retrievers and Spaniels are particularly good. Tala, one of the six dogs used in the test, is a Golden Labrador. His method of indicating a positive sample is to wag his tail furiously, though other dogs used have different ‘tells’. Millie, a Golden Retriever, makes a very particular whining sound. It takes up to 10 weeks to train the dogs.

Will dogs replace mass testing?

No. The research is exciting and interesting, but it has yet to be peer-reviewed and was entirely lab-based. Also the dogs can give false positives, which is problematic: differentiating between a Covid-19 tail wag and a pleased-to-meet-you tail wag isn’t an exact science, it seems. However one massive boon is the speed with which a dog can find a positive sample. In the test, Tala was able to find one in seconds, which is far faster than even the lateral flow tests, and in principle two dogs could sniff their way through a queue of 300 people in about half an hour – very handy for airports and live events such as music festivals. Anyone wagged or whined at could then be asked to take a PCR test.

What’s next?

Scientists now have to have the research checked, and to try to figure out which particular odour particles it is the dogs are detecting. But with similar projects underway in France, Finland and Lebanon, man’s best friend could soon become even more well-liked.