Three days a week, Buffy the yellow Labrador retriever greets visitors at the entrance to Doctors Hospital of Sarasota. If they grant permission, she sniffs their feet, looking for a whiff of active Covid-19 infection. Buffy was trained by Southeastern Guide Dogs as part of a four-dog pilot program for scent detection. They’d originally flunked out of Southeastern’s guide dog training, but they all had another trait in common, never giving up when a treat was hidden somewhere. Three of the four dogs made it through the program training them as Covid detectors. Two of them will remain at the Southeastern campus, where the organization hopes they’ll make it safer for people to return in person.