Sniffer dogs are being tested around the world, including in Australia, to see if they can become the next line of defence against COVID-19.
Just as they are used to detect drugs, explosives, malaria and some cancers, so preliminary research suggests they may be able to detect COVID-19 even when a person has no symptoms.

It is hoped they will supplement existing tests. Ideally, they could be walked though crowds to sniff out people with COVID-19 in stadiums, malls, schools, airports and train stations. They could also be useful in hospitals and quarantine locations.
Researchers from the University of Adelaide’s school of animal and veterinary sciences, who are part of an international alliance to train sniffer dogs to detect COVID-19 infection in sweat, are expected to release results of their research this week.
They have been co-ordinating the Australian arm of the alliance, comparing Australian dogs' ability to detect volatile organic compounds (VOCs) induced by COVID-19 with standard diagnostic laboratory testing.
The international team, led out of the National Veterinary School in Alfort, France, has preliminary results showing specialised working dogs can detect these VOCs with an 83 per cent to 100 per cent success rate.
But, apart from one published pilot study from Germany, all the research to date is preliminary, according to a news report in the journal Nature.
Several studies have been placed on early preprint platforms, but have not yet been peer reviewed. While there is optimism in the field, scientists caution against making big claims from small data sets, under pandemic pressure.
High success rate
In the German pilot, eight dogs from the armed forces identified 83 per cent of positive cases and 96 per cent of negative ones.
Early this month, a group called International K9 Team held an online workshop to share preliminary results and devise methods for co-ordinating research.
It heard dogs in Finland and Lebanon identified cases days before conventional tests picked up the virus, suggesting they may detect infection before symptoms develop.
Some illnesses give off distinct patterns of VOCs. As these molecules evaporate, they create a scent that dogs can detect.
While the COVID-19 virus may have a unique VOC signature, it is suggested dogs may detect the hosts' inflammatory response. French researchers found dogs detect the virus in sweat.
Across the globe, coronavirus detector dogs are now being trained in countries including the United Arab Emirates, Chile, Argentina, Brazil and Belgium.
A French–Lebanese project that trained 18 canines used two of its top dogs in a trial at an airport in Lebanon. It reported the animals were 100 per cent accurate in identifying negative cases and correctly detected 92 per cent of positive cases.
Two months ago, sniffer dogs began patrolling Helsinki Airport as part of a four-month trial. And in London, canines from the Medical Detection Dogs facility are being tested for their efficacy in picking up the scent of coronavirus.
For a sniffing trial in the US, researchers from the University of Pennsylvania are now collecting sweat samples from 1000 T-shirts worn overnight by people who have tested positive or negative for COVID-19.
So, does this work put dogs at risk? Early in the pandemic, people feared dogs could contract the virus and spread it to each other, and to humans. Recent studies suggest dogs are not susceptible – the virus cannot replicate in them.
