Virus World

Canines seem to detect coronavirus infections with remarkable accuracy, but researchers say large-scale studies are needed before the approach is scaled up. Asher is an eccentric, Storm likes sunbathing and Maple loves to use her brain. All three could play a part in controlling the COVID-19 pandemic, but they are not scientists or politicians. They are dogs.  And they are not alone. Around the world, canines are being trained to detect the whiff of COVID-19 infections. Dog trainers are claiming extraordinary results — in some cases, they say that dogs can detect the virus with almost perfect accuracy. Scientists involved with the efforts suggest that canines could help to control the pandemic because they can screen hundreds of people an hour in busy places such as airports or sports stadiums, and are cheaper to run than conventional testing methods such as the RNA-amplification technique PCR. But most of these findings have not yet been peer reviewed or published, making it hard for the wider scientific community to evaluate the claims. Researchers working on more conventional viral tests say that initial results from dog groups are intriguing and show promise. But some question whether the process can be scaled up to a level that would allow the animals to make a meaningful impact. On 3 November, groups working with the animals met in an online workshop called International K9 Team to share preliminary results from experiments and to improve how their research is coordinated. “No one is saying they can replace a PCR machine, but they could be very promising,” says veterinary neurologist Holger Volk at the University of Veterinary Medicine Hanover in Germany, who is leading an effort to train and study COVID-sniffing dogs and did not speak at the event.

Sense of wonder

Humans have taken advantage of canines’ superior sense of smell for decades. Dogs’ noses bear 300 million scent receptors, compared with humans’ 5 million or 6 million. That enables them to detect tiny concentrations of odour that people can’t. Sniffer dogs are already a familiar sight in airports, where they detect firearms, explosives and drugs. Scientists have also trained dogs to detect some cancers and malaria, but the animals are not routinely used for this purpose. Researchers don’t know for sure what the dogs are smelling, but many suspect that these illnesses cause the human body to let off a distinct pattern of volatile organic compounds (VOCs). These molecules readily evaporate to create scent that dogs can pick up. Previous work with non-COVID viruses has suggested that viral infections might also cause the body to do this.  Many sniffer-dog scientists turned their attention to COVID-19 early in the pandemic. They have trained their canines to smell samples, most often of sweat, in sterile containers, and to sit or paw the floor when they detect signs of infection. Trials at airports in the United Arab Emirates, Finland and Lebanon are using dogs to detect COVID-19 in sweat samples from passengers; these are then checked against conventional tests. According to data presented at the K9 meeting, dogs in Finland and Lebanon have identified cases days before conventional tests picked up the virus, suggesting that they can spot infection before symptoms start. Riad Sarkis, a surgeon and researcher at Saint Joseph University in Beirut, is part of a French–Lebanese project that has trained 18 dogs. Sarkis used the best two performers for the airport trial in Lebanon. The dogs screened 1,680 passengers and found 158 COVID-19 cases that were confirmed by PCR tests. The animals correctly identified negative results with 100% accuracy, and correctly detected 92% of positive cases, according to unpublished results. “This is very accurate, feasible, cheap and reproducible,” says Sarkis, who has been approached about using the dogs in schools, banks and prisons, and is working with a shopping mall to offer COVID-19 testing using the animals. Low-income countries with limited lab space could particularly benefit from the approach, says Isabella Eckerle, a virologist at the University Hospitals of Geneva in Switzerland....

Published in Nature (Nov. 23, 2020):

https://doi.org/10.1038/d41586-020-03149-9

In a Finnish study, dogs learned to recognize the distinctive odor of a coronavirus infection. In the future, dogs might be able to detect infected people in nursing homes or at airports. In a pilot study at the University of Helsinki, dogs trained as medical diagnostic assistants were taught to recognize the previously unknown odor signature of the COVID-19 disease caused by the novel coronavirus. And they learned with astonishing success: After only a few weeks, the first dogs were able to accurately distinguish urine samples from COVID-19 patients from urine samples of healthy individuals. "We have solid experience in training disease-related scent detection dogs. It was fantastic to see how fast the dogs took to the new smell," says DogRisk group leader Anna Hielm-Björkman. After only a short time, the animals identified the urine of people infected by the novel coronavirus, known as  SARS-CoV-2, almost as reliably as a standard PCR test. The Finnish scientists are now preparing a randomized, double-blind study in which the dogs will sniff a larger number of patient samples. Only then will the scent tests be used in clinical practice.

The very rapid and promising findings from Finland are also important for other research teams, such as those in Great Britain and France, who are training sniffer dogs to detect COVID-19. Fellow researchers from the German Assistance Dog Center (TARSQ) have also benefited from the Finnish results. "No one could tell us with certainty whether training with the aggressive virus is dangerous or not for humans and dogs. We wanted to gather more information first before we started training because the German virologists advised us against it — after all, so little is known about the virus so far," explains Luca Barrett from TARSQ.

It is still unclear which substances in urine produce the apparently characteristic COVID-19 odor. Since SARS-CoV-2 not only attacks the lungs, but also causes damage to blood vessels, kidneys and other organs, it is assumed that the patients' urine odor also changes. This is something which the dogs, with their highly sensitive olfactory organs, notice immediately. Certain diseases appear to have a specific olfactory signature that trained dogs can sniff out with amazing accuracy, Barrett says. "According to one study, dogs can detect breast cancer with a 93% probability, for example. And lung cancer with a 97% probability," she says.

See also study in BMC Inf. Dis. (July 23, 2020):

https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-020-05281-3

Starting Wednesday, Finland launches a coronavirus-sniffing-dog pilot program at Helsinki Airport. The voluntary tests will reportedly deliver results in seconds, will require no contact with the dogs and take less than a minute of travelers' time. The voluntary canine tests will deliver results within 10 seconds, and require less than a minute of travelers’ time, said Anna Hielm-Björkman, a researcher at the University of Helsinki who is using the trial to gather data. Researchers in other countries, including the United States and the United Arab Emirates, are studying canine coronavirus tests. But the Finnish trial is among the largest in scale and furthest along. In Dubai, health officials this summer began using dogs to analyze sweat samples from randomly selected air travelers, with more than 90% accuracy, according to initial results.

Changes in health can affect the way people smell, researchers say. Dogs long have been valued for their ability to sniff for drugs and bombs, and have proved able to detect cancers, infections and other health problems. Researchers at the University of Helsinki this year found indications that dogs can detect the virus. Scientists say only large-scale trials, such as the one to begin Wednesday, can demonstrate how effective the method will be in practice. As in Dubai, the dogs to be deployed in Helsinki will sniff sweat samples and will not come into contact with travelers. People who agree to the test will swab their necks to produce a sample, to submit through an opening in a wall, said Hielm-Björkman. Regardless of whether they test positive, they will be urged to take a standard polymerase chain reaction (PCR) COVID-19 test so researchers can monitor the dogs’ accuracy. All tests are free for travelers arriving at the airport. Hielm-Björkman said the dogs, according to preliminary research, may be better at detecting coronavirus infections, which can cause the illness COVID-19, than PCR and antibody tests. They “can also find [people] that are not yet PCR positive, but will become PCR positive within a week,” she said. Virpi Perälä, a representative for Evidensia Elainlaakaripalvelut, a network of veterinary clinics that funded the first stage of the trial, during which the initial cohort of dogs were trained, said more funding would be needed to grow the project, depending on initial results.

Out of the 16 dogs trained, four are ready to work. Six others are still in training, with another six found to be unsuitable for a noisy airport environment. Experts have warned that canine tests, however effective, can be difficult to scale. Training is time-consuming and expensive. Even so, researchers are optimistic that it will come to play a roll, even if it cannot alleviate the demands on the world’s strained testing systems. One of the aims of the upcoming trial, said Hielm-Björkman, is to gather observations on how long the dogs can work in shifts. “You see very easily on a dog when it starts to get tired,” she said.