According to the World Health Organization (who), more than 19.7 million people worldwide have been infected with the new coronavirus, which may exceed 20 million this week. In all parts of the world, how to control the spread of the epidemic, and how to gradually restore normal life while controlling the spread of the epidemic, is a topic of great concern to people. We know that rapid detection of new coronavirus infection, isolation of infected patients and tracking and isolation of people they have contacted are one of the important means to control the spread of the epidemic. In order to develop a more rapid and convenient detection method of new coronavirus, many scientists explore the application of a variety of innovative technologies in the detection of new coronavirus, including new generation sequencing technology (NGS), CRISPR gene editing technology, isothermal PCR technology, microfluidic technology and so on. However, some scientists have turned their attention to the dog, the “best friend” in human history. Recently, a German research team published an exploratory study in the journal BMS infectious disease. After only one week of training, eight dogs were able to find saliva or tracheobronchial secretion samples from patients with new coronavirus infection in a randomized, double-blind, controlled trial. The sensitivity and specificity were 82.63% and 96.35%, respectively. The research has sparked widespread media debate. So, can dog detection really become a rapid and effective detection method for new coronavirus? < / P > < p > as we all know, dogs have a very sensitive sense of smell, and people have used this to train dogs to search for many things by smell. For example, drug search dogs, search for missing people’s life-saving dogs, can find hidden objects or people through smell. As early as 1989, the lancet magazine published an article using dog’s smell to detect melanoma. Scientists have also known for a long time that diseases cause changes in the composition of volatile compounds secreted by people, which forms the basis for using dogs’ sensitive noses to detect diseases. < / P > < p > in this study, eight dogs were trained using samples of patients with covid-19 who were diagnosed with symptoms and who were not infected with the new coronavirus by RT-PCR. If they were able to identify one of the seven samples that belonged to a covid-19 patient, they would be rewarded. After training, the dog’s ability to detect the virus increased from 19% to 7% on the second day. < / P > < p > after training, the 8 dogs received a randomized, double-blind, control group test. The researchers randomly provided the dogs with samples from patients with covid-19 or without new coronavirus. After 1012 random and automated sample presentation, 157 positive samples, 792 negative samples, 33 false positive samples and 30 false negative samples were found in 8 dogs. After calculation, the diagnostic sensitivity was 82.63% (95% CI, 82.02% – 83.24%) and the specificity was 96.35% (95% CI: 96.31% – 96.39%). The detection specificity of all 8 dogs had little change, but their detection sensitivity was quite different. < / P > < p > in the discussion section of the article, considering that the current “gold standard” RT-PCR for detection of new coronavirus infection also has a false-positive rate of 2.3-6.9%, the performance of detection dogs is worthy of recognition. If the detection method is improved, it may become an effective method for rapid screening of new coronavirus infection by assisting or replacing RT-PCR. < / P > < p > recently, scientists in the UK have launched a study to test whether six dogs can accurately detect asymptomatic patients infected with new coronavirus after eight weeks of training. The researchers envision that they could become a rapid, non-invasive means of detecting asymptomatic infections at airport checkpoints. < / P > < p > since the detection dogs have performed well in finding positive samples of new coronavirus, will they be seen in public places such as airports in the future? The researchers say real-world applications are very different from the environments in scientific research, adding to the challenge of detecting dog performance. It is necessary to use positive reinforcement to train dogs to detect new coronavirus positive samples or missing persons. Simply put, when the dog chooses the right target, it will receive positive encouragement or reward. It may be toys or food. In the process of the experiment, because there are always positive samples of new coronavirus, and the researchers can reward the dogs in a short time after they make a correct judgment, so they can be actively strengthened. < / P > < p > however, in real-world applications, testing dogs may need to find a positive sample out of thousands of negative samples, which can be a boring job for them without reward. What’s more, in the real world, even if the dogs make the right choice, they can’t confirm whether they have made the right choice (because other tests such as RT-PCR are needed to confirm the samples found by the dogs). This kind of delay will lead to the dog can not be rewarded in time after making the right choice, thus “hitting” their enthusiasm. < / P > < p > as mentioned earlier, the concept of using detection dogs to detect cancer patients has a long history, but at present, the use of detection dogs to screen cancer has not been widely used. In 2017, Dr. Klaus hackner, an Austrian scholar, published an article on the Journal of breath research. He pointed out that in the scenario of simulating the real world (researchers did not know which sample was positive in advance, and could not reward the testing dog in time), the performance of detection dogs in detecting cancer samples was not good. < / P > < p > in addition, there are other challenges in the detection of new coronavirus infections with detection dogs. For example, the physiological status of trained dogs will fluctuate, which will directly affect the accuracy of their detection. Moreover, whether the positive samples of new coronavirus can infect dogs is still a question that has not been answered. If dogs are infected with the new coronavirus, will their sense of smell be affected, and will they become a new source of infection? < / P > < p > diseases can lead to changes in the composition of volatile organic compounds (VOC) in patients’ samples, which is the fundamental reason why dogs can find disease samples. If we can find the changes of VOC characteristics caused by new coronavirus infection, we may design an electronic nose to simulate the detection dog for rapid detection. Using gas chromatography combined with ion mobility spectrometry, researchers can distinguish patients with new coronavirus from patients with influenza A by detecting breath samples from patients, according to a proof of concept study published by German researchers on the preprint website medrxiv. < / P > < p > even if dogs can not quickly become an effective method for rapid detection of new crowns in the real world, they may still help scientists find VOC characteristics related to different diseases, thus contributing to the design of more effective and convenient non-invasive disease detection methods.