Dogs are known for a sense of smell so acute they have the ability to detect cancer, monitor diabetes and screen for an array of infectious diseases. Recently, several groups around the world have demonstrated that dogs are also able screen individuals for COVID-19 infections.
Beginning in September 2021, the CDC Foundation partnered with the Association of Public Health Laboratories (APHL), Early Alert Canines and the California Department of Public Health to acquire and train two Labrador retrievers to detect COVID-19 infections in congregate settings, and are already applying their skills in school settings.
Scarlett and Rizzo, COVID-19 detection dogs, were trained by Early Alert Canines to smell and detect COVID-19 infection. When a person is positive for COVID-19, they produce unique volatile organic compounds (VOCs) that the dogs are trained to detect using socks worn by previously tested COVID-19 infected individuals.
For the training, the dogs were presented with various scents through a device called a scent wheel. The wheel offered the canines a multiple-choice scenario of odors and helped to desensitize them to non-target odors they may encounter during searches. During eight weeks of initial training, Scarlett and Rizzo correctly identified positive socks in over 90 percent of the trials.
After the first phase of training was complete, the two dogs began visiting school sites in the San Francisco Bay Area, where they screen individuals for the scent of COVID-19 infection. For such screenings, students and staff line up, typically outside, and the dogs are led by handlers to sniff the ankles and shoes of each participant. If they detect COVID-19, the dogs alert their handlers by sitting down next to suspected infected person. Anyone the dogs screen is tested with a rapid antigen test to verify the results of the dog screening.
Since the inception of the program, Scarlett and Rizzo have visited many school campuses and screened more than 1,804 unique individuals–4,064 total screenings. Compared to rapid antigen testing, Scarlett is able to detect between eight to nine out of every 10 infections found by antigen while Rizzo detects eight of 10.
In cases where a dog identifies a person as positive but the antigen test is negative, a follow-up PCR done same day or consecutive antigen tests are done the following days to verify results. Interestingly, the dogs have sometimes caught positive cases before the antigen test.
“We've had a few instances where the dogs have indicated on somebody and that day their immediate antigen comes out negative, and within the following day or two you get a positive antigen or PCR confirmation,” said Alysia Santos, Scarlett’s handler. “It seems that we have been able to catch it earlier [with the dogs].”
Having access to the detection dogs gives schools tremendous flexibility. Not only have the dogs been used to screen school students before and after proms to catch outbreaks, but they have also been used in special needs school programs where many students are often unable to self-swab, allowing schools to have a positive and individualized interaction with these students while also receiving accurate test results.
“I could go on and on about the impact [the detection dogs] had on our programs,” said one representative from a special needs program that worked with the dogs. “Our students with disabilities asked questions and talked about it for days at school and, according to a partner, at home as well.”
In addition to being accurate in their detections, survey results show dogs are more popular than traditional testing methods. One participant said, “I think the dogs provide valuable information in a noninvasive manner that can be used to narrow down people who should test further.”
To date, 100 percent of schools who used the dogs responded that both children and parents were receptive to the program. All of the participating schools also asked to continue the dog screening process within their COVID-19 testing programs.
Slated to continue into September 2022, this type of COVID-19 screening is less invasive than other methods and deserves further study for widescale implementation. As the project explores ways to use the dogs in even larger congregate settings, Scarlett, Rizzo and the partners that made this project possible will continue to provide schools with a unique approach to keeping their students, faculty and staff safe from COVID-19.