Can Dogs Sniff Out Coronavirus Infections?

It would seem that dogs can recognize coronavirus infections with extreme precision. But science is cautious, stating that large-scale studies are needed to arrive at a definitive answer

(photo: Suzzamar / pixabay) That dogs have an amazing sense of smell is nothing new. But that they can sniff and identify coronavirus infections with near-perfect accuracy would be an extraordinary achievement. Yet, all over the world, there are more and more studies that tell of this great ability of dogs, teasing many the idea that animals can actually help us control the Covid-19 pandemic. However, a great deal of caution is still needed: most of these experiments, in fact, have not yet been reviewed or published, and therefore have not been evaluated by the scientific community.

Just to realize, we human beings are equipped with about 5-6 million olfactory receptors, while dogs have as many as 300 million, which allow them to detect even the smallest concentrations of odors. An extraordinary ability that we have been exploiting for some time: just think that sniffer dogs, which we often see in places like airports, can detect firearms, explosives and drugs. But not only that: dogs are also capable of identifying certain types of cancer, malaria and other viral diseases, although it is not yet clear what the precise mechanism is. Many experts, for example, hypothesize that some diseases cause the body to release specific volatile organic compounds (Cov), the molecules of which evaporate to create a smell that dogs can recognize.

Coma tells Nature, in recent days the different groups of scientists who are working with these animals to understand their ability to identify the coronavirus have gathered at the International K9 Team, an online conference that has allowed share the preliminary results of the various experiments. From the meeting it emerged that in several tests carried out at airports in the United Arab Emirates, Finland and Lebanon, dogs identified coronavirus positive cases days earlier than conventional tests, thus suggesting that they can detect the infection before symptoms begin. In experiments carried out by researchers at the Saint Joseph University of Beirut, for example, 18 dogs were trained to smell sweat samples from infected people and sit down whenever they detected signs of infection. From here, the dogs sniffed around 1,600 airport passengers, finding 158 coronavirus positive cases confirmed by molecular tests. In particular, according to the unpublished data, they managed to correctly identify positive cases with an accuracy of 92%.

"No one is saying they can replace PCR, but their help could be very valuable" Holger Volk, a veterinary neurologist at the University of Hanover, in Germany, tells Nature. In his study, the only one to have been published so far, 8 dogs were trained on samples taken from the respiratory tract of 7 coronavirus positive people and another 7 healthy. The dogs, explains the expert, identified 83% of positive and 96% of negative cases.

Some experts, however, have been skeptical of these results, stating that the number of participants was too small and that dogs could have learned to identify the specific smell of the samples, rather than that of the coronavirus. Although, therefore, the data is promising, it would need to be confirmed on a much larger scale in order to assess how much dogs can actually help us in detecting positive cases. "It is important not to publish too early with large claims and small data sets," concludes James Logan, an infectious disease specialist at the London School of Hygiene & Tropical Medicine.