Sniffer dogs detect COVID-19 infections with 94 percent accuracy

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Dogs have an acute sense of smell. They have up to 300 million olfactory receptors in their noses, compared to six million in humans, making their smell receptors up 10,000 to 100,000 more powerful than humans. The part of a dog's brain that is devoted to analyzing smells is, proportionally speaking, 40 times greater than humans. Trained sniffer dogs can detect diseases such as malaria, cancer, and even viral infections.

Now, a team of German researchers at the University of Veterinary Medicine Hanover, the German Armed Forces, and the Hannover Medical School revealed that dogs can discriminate between human saliva samples infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and non-infected samples with a 94 percent overall success rate. Their research is published in the journal BMC Infectious Diseases.

Accurate and reliable

To arrive at their findings, the team trained eight detection dogs to sniff out SARS-CoV-2-infected samples for one week. The training aims to hone the smelling power of the dogs to detect saliva or tracheobronchial secretions of infected patients in a randomized, double-blinded, and controlled study.

The trained dogs sniffed the saliva of more than 1,000 people that were either healthy or infected with the virus. The samples of coronavirus disease (COVID-19) patients were distributed at random.

During the study, the dogs achieved an overall average detection rate of 94 percent with 157 correct indications of positive, 792 correct rejections of negative, 33 incorrect indications of negative or incorrect rejections of 30 positive sample presentations.

"These preliminary findings indicate that trained detection dogs can identify respiratory secretion samples from hospitalized and clinically diseased SARS-CoV-2 infected individuals by discriminating between samples from SARS-CoV-2 infected patients and negative controls. This data may form the basis for the reliable screening method of SARS-CoV-2 infected people," the researchers concluded in the study.

Diagnoses by dog noses – Dogs can sniff out patients with COVID-19

Differentiating smell

The team emphasized that the timely and accurate detection of SARS-CoV-2 infected people is critical for countries to contain the spread of the pandemic. The research findings indicate that dogs can be trained in just about a week to differentiate between samples of people infected and non-infected with SARS-CoV-2.

The researchers believe that dogs can detect infected samples because people who get infected have changes in their metabolic processes.

"We think that the dogs can detect a specific smell of the metabolic changes that occur in those patients," Maren von Koeckritz-Blickwede, a professor at the university, who conducted the study, said in a video.

The team hopes that the method can be used amid the pandemic, to help control the virus spread and reduce the number of cases, which has now topped 16.66 million across 188 countries and territories.

"The current study results are promising, although they should be regarded as preliminary, and suitability for this detection method in the field can only be acquired after further research has been conducted. Our work provides the very first steps of the development of a new SARS-CoV-2 screening method," the researchers said.

Further, the researchers added that in countries with limited access to diagnostic tests, detection dogs could be used for mass detection of people infected with the novel coronavirus.

The use of detection dogs has made its debut in Chile. Police dogs are being trained to identify infected people, even in the earliest stages of the disease.

In England, six dogs are being trained by Medical Detection Dogs in Milton Keynes to sniff out and detect the presence of the virus. Dr. Claire Guest, the charity's co-founder and chief executive, said that the dogs had shown signs that they would be able to detect the virus. She has previously trained dogs to detect the scent of other diseases, such as cancer, Parkinson's disease, and malaria.

The dogs, named Digby, Norman, Jasper, Star, Storm, and Asher, will be trained to smell samples on sterilized socks, stockings, and face masks worn by NHS staff in London. The training team expects about 3,200 samples and will use them for training the dogs.

The team believes that when they train dogs to detect the virus, they can help contain its spread.


Journal reference:
Angela Betsaida B. Laguipo

Written by

Angela Betsaida B. Laguipo

Angela is a nurse by profession and a writer by heart. She graduated with honors (Cum Laude) for her Bachelor of Nursing degree at the University of Baguio, Philippines. She is currently completing her Master's Degree where she specialized in Maternal and Child Nursing and worked as a clinical instructor and educator in the School of Nursing at the University of Baguio.


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  1. Jim Barron Jim Barron United States says:

    The numbers are inconsistent:

    " 33 incorrect indications of negative or incorrect rejections of 30 positive sample presentations"

    An "incorrect indication of negative" is exactly the same thing as an  "incorrect rejection of positive"   so if the wording was correct they both should have been the same number.   Obviously the wording was in error but it's not clear what the error was.

    While 33 is close to 30, the difference is not great, but still ...     The inaccuracy makes it impossible to calculate directly the rate of false positives and rate of false negatives.

    False negatives probably wouldn't be much of a problem because
    1) they'd likely be due to a case where a person was not yet enough infected for metabolic changes to have occurred at a level detectable to the dogs  - so if the test was relied on for only a short time frame (3 hour flight, etc)  they've be much less likely to infect someone else than most cases
    2)   even if you miss a few very early, and therefore weakly infective cases, using the dogs would obviously greatly reduce the spread of the infection, since it's all about getting the ROI (rate of infection) down and the dogs would unquestionably accomplish that.

    A potential problem with false positives is what is done with them.   If they are grouped together, you'd be almost assuring that the false positives would then become true positives.

    Both the 30 and 33 are false negatives (AS STATED).  It either of them was actually false positives then the false positive rate is around 20%.       So for every 4 (or so) infected individuals you isolate, you would be mixing one actually uninfected person in with them.    IF they are kept isolated from each other that's not a problem.    Because of the high rate of false positives they should be, but WILL they be?

  2. Jim Barron Jim Barron United States says:

    PS   The most likely reason for sniffer dogs doing a false positive would presumably be some other medical condition(s) that caused some of the same metabolic imbalances/products as COVID-19.     Since most medical conditions make one more vulnerable to COVID-19, the apparently high rate of false positives would make it highly important to keep those the tests identify as positive isolated FROM EACH OTHER, at least until a more accurate test (with a low rate of false positives) was done.

    IMHO the haphazard manner in which measures have been implemented in many places (most especially in the United States) and the lack of understanding or outright denial of many government officials, makes it imperative that those distributing sniffer dogs, if this is done widely, make it very clear that it is critical to keep people the dogs identify as positive isolated from each other until a more accurate test is done.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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