Abstract
While the world awaits a widely available COVID-19 vaccine, availability of testing is limited in many regions and can be further compounded by shortages of reagents, prolonged processing time and delayed results. One approach to rapid testing is to leverage the volatile organic compound (VOC) signature of SARS-CoV-2 infection. Detection dogs, a biological sensor of VOCs, were utilized to investigate whether SARS-CoV-2 positive urine and saliva patient samples had a unique odor signature. The virus was inactivated in all training samples with either detergent or heat treatment. Using detergent-inactivated urine samples, dogs were initially trained to find samples collected from hospitalized patients confirmed with SARS-CoV-2 infection, while ignoring samples collected from controls. Dogs were then tested on their ability to spontaneously recognize heat-treated urine samples as well as heat-treated saliva from hospitalized SARS-CoV-2 positive patients. Dogs successfully discriminated between infected and uninfected urine samples, regardless of the inactivation protocol, as well as heat-treated saliva samples. Generalization to novel samples was limited, particularly after intensive training with a restricted sample set. A unique odor associated with SARS-CoV-2 infection present in human urine as well as saliva, provides impetus for the development of odor-based screening, either by electronic, chemical, or biological sensing methods. The use of dogs for screening in an operational setting will require training with a large number of novel SARS-CoV-2 positive and confirmed negative samples.
Highlights
COVID-19, the respiratory infection resulting from SARS-CoV-2 infection, is responsible for the global pandemic starting winter of 2019, with a current infection fatality ratio estimated at 0.5–1% [1, 2]
Though dogs have previously been shown to be able to discriminate between saliva samples of SARS-CoV-2 positive and negative patients [19], these studies are using repeated presentations of the same samples
It is possible that the result is that dogs are able to discriminate between their training set of positive and negative patient samples but are unable to generalize this odor to new samples
Summary
COVID-19, the respiratory infection resulting from SARS-CoV-2 infection, is responsible for the global pandemic starting winter of 2019, with a current infection fatality ratio estimated at 0.5–1% [1, 2]. The rapid spread of the disease has been furthered by limited availability of reagents, low levels of testing and slow turnaround times for results, which makes contact tracing of infected individuals effectively impossible at levels necessary to contain the virus [4]. In order to effectively quarantine infected individuals, cost-effective, rapid, diagnostic tests with high sensitivities (true positive rates) and specificities (true negative rates) are necessary. RT-PCR testing has a high specificity, but false negatives can result from challenges with sampling and false positives may result from the presence of viral RNA without replication-competent virus
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