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Belgian shepherd Filou was among those used in new research that has demonstrated that sniffer dogs can detect cases of Long Covid. Ole Spata/dpa

Sniffer dogs, which have been trained to detect people infected with the coronavirus since the start of the pandemic, can also tell when a person has Long Covid, researchers in Germany have found.

A team led by the University of Veterinary Medicine Hannover (TiHo) found that certain compounds that remain present in Long Covid patients long after the initial infection can be picked up by dogs.

Sniffer dogs have already been used at airports and public events to help detect coronavirus infections and prevent super-spreader events, and researchers now hope dogs will be able to help spot unidentified Long Covid cases.

“It is known that infectious respiratory diseases can release specific volatile organic compounds,” said Holger Volk, head of the TiHo clinic for small animals, who published the study in the journal Frontiers in Medicine.

Dogs in their trials were able to detect these compounds, the researchers said, even when PCR tests are negative and antibody tests can no longer provide information about the disease.

In mid-2020, the TiHo researchers published a first study on sniffer dogs that had been trained to identify infected people through samples of saliva and respiratory secretion. A follow-up study showed that sweat and urine are also suitable sample material.

According to TiHo virologist Claudia Schulz, the sniffer dogs’ extraordinary diagnostic ability makes it possible to optimise the treatment of those affected.

In various test scenarios, the scientists in the new study showed nine sniffer dogs samples from Sars-Cov-2 infected persons, with Long Covid samples as well as with negative samples.

When the dogs were presented with samples from Long Covid patients and, for comparison, samples from healthy people, they recognised the patient samples in over 90% of the tests.

In addition to helping identify Long Covid, dogs are increasingly being used to recognise different types of cancer, malaria and some bacterial and viral infections.