Could dogs help in the fight against Covid-19? Some scientists think so. Several groups currently are training canines to use their sensitive noses to detect the disease.

A dog can have as many as 300 million olfactory receptors in its nose. Airborne odor molecules bind to these structures. That allows dogs to smell even the faintest scents—like those given off by people infected with the virus that causes Covid-19.

These trained super-sniffers could check people for Covid-19 in crowded places like airports, says Claire Guest. She’s the chief scientific officer of Medical Detection Dogs, an organization training dogs to detect Covid-19. “At the moment, there’s no other way to screen so many people so quickly,” says Guest.