June 15, 2021

Results of a recent study suggest people with COVID-19 produce a scent that is identifiable by trained detection dogs.

The researchers plan further study in hopes they could develop detection dogs that would help protect people at public gatherings.

An announcement from the University of Pennsylvania School of Veterinary Medicine indicates nine detection dogs tested in a study involving urine samples identified SARS-CoV-2 infection with 96% accuracy. School officials said those results would be used in a subsequent investigation into whether dogs can be trained to distinguish between body odors of people who are positive for SARS-CoV-2 infection, negative for infection, or vaccinated.

An announcement from Penn Vet indicates the study results support the existence of an odor that is produced by humans in response to SARS-CoV-2 infection and is detectable by dogs.

An article describing the results, published April 14 in PLOS One, a journal from the Public Library of Science, states that the researchers procured saliva and urine samples from hospitalized children and adults who were positive for SARS-CoV-2. They also received control samples from SARS-CoV-2–negative patients at the same children’s hospital and from adult volunteers who had negative tests for SARS-CoV-2 and lacked COVID-19 symptoms. The research team tested the dogs using samples from infected individuals, samples from controls, and distraction scents such as garlic, marinade, and marker ink on paper.

The article indicates that dogs initially performed well but, with intensive training on a limited number of samples, the dogs appeared to shift from generalization to focusing on individual odors in the training set. The dogs also repeatedly focused on scents of one person who had recovered from COVID-19 and another who had recently had COVID-19 symptoms, although both had negative test results for SARS-CoV-2 by real-time polymerase chain reaction–based assays.

The follow-up study will examine the ability of dogs to discriminate among odors of people who are COVID-19–positive, COVID-19–negative, or vaccinated using T-shirts those people wear overnight. Dr. Cynthia M. Otto, director of the Penn Vet Working Dog Center, said in the announcement that the study would involve at least hundreds of samples in hopes the study conditions would more closely reflect what the dogs would encounter in a community setting.

Dr. Otto said in a message that her research team is uncertain whether the scent detected by the dogs is unique to SARS-CoV-2, which is why the follow-up study involving people participating from their homes is important.

“The more people we get to participate, the better we will know that it is specific,” she said.

The follow-up study will let the team include participants who are negative for SARS-CoV-2 infection but have similar symptoms.