The fight against the coronavirus pandemic has scientists tapping an unlikely resource: the finely tuned olfactory sense of bees.

Dutch researchers on Monday said they have trained honeybees to stick out their tongues when presented with the virus’s unique scent, acting as a kind of rapid test.

Although it’s a less conventional method than lab tests, the scientists said teaching bees to diagnose the coronavirus could help fill a gap in low-income countries with limited access to more sophisticated technology, like materials for polymerase chain reaction (PCR) tests.

“Not all laboratories have that, especially in smaller-income countries,” said Wim van der Poel, a professor at Wageningen University, which led the research. “Bees are everywhere, and the apparatus is not very complicated.”

The scientists trained roughly 150 bees with a Pavlovian conditioning method in which they gave the insects a sugar-water solution each time they were exposed to the smell of the coronavirus. When the bees were presented with a sample that was negative for the virus, they received no reward.

After repeatedly extending their tongues — technically called proboscises — for the sugar water, the scientists said the bees learned to stick out their tongues for a positive sample, even with no reward offered. Within hours, the insects were trained to identify the virus a few seconds after encountering it, the researchers said.

While the research continues, van der Poel said the scientists believe they can achieve about a 95 percent accuracy rate if they use multiple insects to sniff each sample. Their results have not yet been published or peer-reviewed.

“Our first goal was to demonstrate that we could train bees to do this, and that’s where we succeeded,” van der Poel said. “And now we are calculating, and we are continuing the work to see how sensitive the method is.”

The idea for the research sprang from the founders of Dutch insect-technology start-up InsectSense, who had previously used bees to detect mineral-rich ore and land mines. When staff realized they could also train bees to find the coronavirus, they looped in the university researchers.

Each time the scientists wanted to train a new set of bees, they used a refrigerator or the natural external temperature to cool them down and make them less active, van der Poel said. Then they put the bees in harnesses so they would stay still while confronted with the samples, which consist of the respiratory material from a nasal swab mixed with chemicals.

The bees smelled samples from both minks and humans, and were similarly good at identifying the virus in both situations, van der Poel said.

InsectSense said it is working on a machine that could train multiple bees simultaneously to make the diagnoses, as well as a biochip that would use genes from the cells that bees smell with to detect the virus. That method would circumvent the need to use live insects, which van der Poel said might be impractical on a large scale.

“If this is going to work, it can be very fast and very cheap,” van der Poel said. “And that would be very convenient.”

While researchers are also examining whether dogs could be used to detect the coronavirus, van der Poel said he thought scientists could more easily test samples with several bees than several dogs, given the relative ease of handling bees. A study published by the University of Pennsylvania last month suggested that dogs can detect the coronavirus with 96 percent accuracy.

Dirk de Graaf, a professor who studies bees at Ghent University in Belgium, told Reuters he was skeptical that coronavirus-sniffing bees would replace lab tests.

“It is a good idea, but I would prefer to carry out tests using the classic diagnostic tools rather than using honeybees for this,” he said. “I am a huge bee lover, but I would use the bees for other purposes than detecting covid-19.”

In addition to identifying diseases, animals — including dogs, wasps and grasshoppers — have long been used to detect explosives. Researchers working for the U.S. Department of Defense began to study the concept, known as “insect sniffing,” in the late 1990s.

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