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(THE CONVERSATION) Editor's note: As COVID-19 continues to spread worldwide, scientists are analyzing new ways to track it. One promising approach is training dogs to detect people who are infected by smelling samples of human urine or sweat. Research scientist Glen Golden, who has trained dogs and ferrets to detect avian flu in birds, explains why certain animals are well suited to sniff out sickness.

1. Which species have a nose for disease?

Some animals have highly developed sen...