Can dogs sniff out COVID-19 infected people? Will it replace nucleic acid testing? increased knowledge
Do you know how sensitive a dog's sense of smell is? In terms of data, it is about 1 million times that of humans. Humans have about 5 million olfactory cells, compared with 120 million in dachshunds and 220 million in sheepdogs.
Some studies have shown that dogs can detect a variety of diseases, even cancer. Sniffer dogs can warn of diabetes, epilepsy, stroke, Parkinson's, and more.
Now that the COVID-19 epidemic is still raging around the world, can dogs with this sky-defying skill identify people infected with COVID-19 ?
1. Study: Can dogs smell the COVID-19 virus?
A Finnish study found that may have an answer to this question.
In the spring of 2020, the researchers trained four puppies to detect the COVID-19 virus (all four previously trained to sniff out dangerous goods, illegal drugs or cancer).
Between September 2020 and April 2021, 4 puppies sniffed 303 incoming passengers at Finland's international airport while they were tested with PCR dipsticks. In the end, the two matched 296 , and the researchers calculated that based on the prevalence, sniffer dogs can completely replace the traditional PCR swab test.
Previously, in a French-Lebanon cooperation project, 18 dogs were trained, and the 2 best performing dogs were selected to participate in the airport experiment.
The two selected dogs screened a total of 1,680 passengers and found 158 cases of COVID-19 pneumonia confirmed by PCR testing. Currently, dogs may be 100 percent accurate in detecting negative COVID-19 cases and 92 percent accurate in detecting positive COVID-19 cases, based on unpublished results.
Trial participants said: "The use of dogs to test for COVID-19 pneumonia is very accurate, feasible, cheap and reproducible."
2. Will dogs replace nucleic acid testing?
First make two points clear. The first is, what might the dog smell? Is it the COVID-19 virus itself?
The researchers were not sure what the dog smelled, but initially speculated that the disease may cause the human body to release a unique volatile organic compound VOCs , and the odor produced during the volatilization process was smelled by the dog.
Second, according to Dr. Zhou Yebin, an immunology researcher , sensitivity and specificity are key indicators of the quality of a disease detection.
In the detection of COVID-19 pneumonia, the sensitivity and specificity are naturally higher. Among them, RT-PCR in nucleic acid detection has a sensitivity of 97.99% and a specificity of 95% to 99%. In the experiment, the sensitivity and specificity of dogs in the detection of COVID-19 pneumonia may not necessarily surpass nucleic acid detection.
Therefore, from the results, it is temporarily impossible to know whether dogs will replace nucleic acids, but this is undoubtedly a new type of detection mode.
3. Will the use of dogs for large-scale gas detection be promoted?
Dogs have the unique advantage of being able to screen many people in a short period of time. But it may be a little difficult to implement.
First, dogs may suffer from performance impairments due to inability to access rewards in a timely manner.
For dog training, after choosing the right goal, the dog can get encouragement, toys or food for positive reinforcement.
However, in actual combat, the dog may need to find a positive sample among thousands of negative samples, and if there is no reward, this may be a very boring job for the dog.
Moreover, even if the testing dog can make the right choice, the testing personnel still need to re-confirm the positive samples found by the testing dog. This delay may prevent the testing dog from getting the reward in time and discourage the dog's work.
Second, if a dog has COVID-19, will it affect its sense of smell? Will it be contagious? This is also a problem.
Then, there will be more interference factors in practical application . Dr. Yebin Zhou said that , unlike a single molecular signature of a contraband, the COVID-19 "smell signature" is a collection of multiple organic molecules.
Are there other physiological processes unrelated to COVID-19 infection that influence or even override the COVID-19 "smell signature" acquired by trained dogs? For example, if a person infected with COVID-19 has other diseases at the same time, can dogs still smell the odor characteristics of COVID-19?
Finally, COVID-19 itself is extremely complex. Will the "smell signature" brought to the human body be consistent for different COVID-19 mutants?
In short, sniffing out the COVID-19 virus through dogs is more likely to be a preliminary concept in the laboratory, and there is still a distance from practice. However, new forms of detection such as sniffer dogs are indeed worth looking forward to.
References:
[1] "Dogs Can Identify COVID-19 Infected! Do you know what other skills they have in the medical field? 》. Mays Medicine. 2020-06-06
[2] "Can you stop poking your throat in the future? Dogs can sniff out COVID-19 virus with accuracy comparable to nasopharyngeal swab test, study finds
[3] Can dogs really sniff out the COVID-19 virus? See what scientific research says". Nutshell. 2020-12-02
[4] "Do Dogs Sniff Out COVID-19, Is It Reliable?" 》.Intellectuals.2021-05-26
[5] Can Dogs Smell You Have COVID-19? The truth may not be as simple as you think". WuXi PharmaTech.2020-08-11
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