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Scientists in the Netherlands have trained bees to identify COVID-19 through their sense of smell, according to a press release from Wageningen University. The research was conducted on more than 150 bees in Wageningen University’s bio-veterinary research laboratory.

The scientists trained the bees by giving them a treat — a sugar-water solution (溶液) — every time they were exposed to the scent of a mink (貂) infected with COVID-19. Each time the bees were exposed to a non-infected sample, they wouldn’t get a reward. Eventually, the bees could identify an infected sample within a few seconds — and would then stick out their tongues like clockwork to collect the sugar water.

Bees aren’t the first animals to detect COVID-19 by scent. Researchers have also trained dogs to distinguish between positive and negative COVID-19 samples from human saliva (唾液) or sweat with fairly high levels of accuracy. A small German study found that dogs could identify positive COVID-19 samples 94% of the time. That’s because metabolic changes from the coronavirus make an infected person’s bodily fluids smell slightly different from those of a non-infected person. But researchers still aren’t sure whether animals are the best bet (赌注) for sniffing out COVID-19 cases outside the lab.

“No one is saying they can replace a PCR machine, but they could be very promising,” Holger Volk, a neurologist, told Nature. PCR machines are what lab technicians use to process standard COVID-19 swab tests. At the very least, certain animals could be useful for identifying COVID-19 in places or countries in which high-tech laboratory equipment is scarce or inaccessible.

Wageningen scientists are working on a prototype of a machine that could automatically train multiple bees at once. Then bees can use their skills to test for coronavirus aerosols (气溶胶) in the surrounding environment.