Trained scent dogs detect airline travelers with COVID-19

"Sniffer dogs" may be able to use their highly developed sense of smell to single out people infected with COVID-19, regardless of whether they have symptoms, according to a triple-blind randomized validation trial and real-life observations published yesterday in BMJ Global Health.In spring 2020, a team led by University of Helsinki researchers trained four dogs by randomly presenting them with skin swabs from 420 parallel samples from 114 people infected with wild-type SARS-CoV-2 and 306 negative controls over seven sessions.

Each dog had previously been trained to detect illegal drugs, dangerous goods, or cancer.At the Helsinki-Vantaa International Airport, the dogs sniffed skin swabs from 303 incoming passengers also tested for COVID-19 using polymerase chain reaction (PCR) from September 2020 to April 2021.Accuracy greater than 90%Relative to PCR, the canines had an estimated accuracy in detecting SARS-CoV-2 of 92% (95% confidence interval [CI], 90% to 93%), a sensitivity of 92% (95% CI, 89% to 94%), and a specificity of 91% (95% CI, 89% to 93%).

They were much less accurate in detecting infections caused by the Alpha variant (89% for wild-type virus vs 36% for Alpha; odds ratio [OR], 14.0 [95% CI, 4.5 to 43.4]).But the latter finding also illustrates how well dogs can distinguish between different scents, the team said. "This observation is remarkable as it proves the scent dogs' robust discriminatory power," they wrote."The obvious implication is that training samples should cover all epidemiologically relevant variants.

Our preliminary observations suggest that dogs primed with one virus type can in a few hours be retrained to detect its variants."The dogs correctly identified 296 of 300 samples (99%) identified