London School of Hygiene & Tropical Medicine

Innovative science is often borne out of necessity, and this pandemic is no different. Scientists around the world have sequenced the SARS Cov-2 genome, rapidly identified COVID-19 strains and developed successful vaccines in record-breaking time to tackle the virus.

COVID-19 diagnostics, such as PCR and lateral flow tests (LFT), are now an intrinsic part of our everyday lives, helping to detect cases and prevent small, localised outbreaks from becoming epidemics. However, these tools – while crucial – are invasive, costly and do not offer immediate results.

Potential solutions are not always fully in the hands of humans. As scientists, we're tasked with coming up with new ideas and technologies to tackle the world's greatest problems. But often, nature has already done this for us. And the answer is right under our nose. 

Our body odour changes when we are ill.  For example, apparently typhoid smells like baked brown bread. Tuberculosis smells like stale beer, and yellow fever smells like the inside of a butcher shop. We also recently showed that a malaria infection changes your body odour to make you more attractive to mosquitoes. But to be able to use these subtle odour changes as a way of diagnosing a disease, we would need a very powerful detector. And that is where the world’s best biosensors come in – dogs.

For years, our furry companions have played an important role in keeping people safe and supporting law enforcement, sniffing out bombs, drugs, or even banned organic materials. But they can also sniff out disease.

While many of us associate medical dogs as a form of support for people with disabilities, their potential contribution to science goes far beyond that. More than ten years of ground-breaking scientific research by the charity Medical Detection Dogs has shown these super-sniffers can be trained to detect odours associated with infection. They can identify these odours with incredible accuracy, what would be the equivalent of a human detecting one teaspoon of sugar in two Olympic-sized swimming pools of water.

This was the catalyst for a collaboration between our team at the London School of Hygiene & Tropical Medicine, Medical Detection Dogs and Durham University to train dogs to detect the odour associated with a malaria infection, with great success.

Then in February 2020, with COVID-19 spreading worldwide, we began to wonder if COVID-19 infections have a distinct odour, and if dogs could be trained to detect it.

Previous research showed that respiratory diseases change the infected individual’s body odour, so it seemed logical that COVID-19 infection might also have a distinct smell. So, with support from the UK government, we assembled our human and canine team to investigate. The results could not be more exciting.

Through a series of scientifically robust trials we proved that COVID-19 has a distinct odour. Then we put the disease detective dogs to work, and within just a few weeks, the super-sniffers were far exceeding our expectations. They detected the virus in samples donated by the public with good consistency and excellent accuracy, with the best performing dogs detecting odour from an infected individual with up to 94% accuracy.

They could even detect odour from individuals who were asymptomatic, and who were infected with different strains. Importantly, dogs are extraordinarily fast, with each individual dog predicted to screen 300 people within an hour. So what potential benefits could COVID-19 detection dogs bring?

COVID-19 has brought international travel to a near standstill, with countries closing their borders to protect against the new public health threat.

On 17 March 2020, the Foreign and Commonwealth Office officially advised against all non-essential overseas travel. That month Ryanair, Virgin and EasyJet cut their flights by 80%. Between February and April 2020, monthly air passenger arrivals fell by 98.3%.

This sudden drop in international travel has had a devastating effect on the travel industry. May 2020 saw the lowest level in travel and tourism business, reducing the economic output for aviation by 90% between February and December 2020. Around 160,000 jobs in the industry have been lost during the pandemic.

Dogs trained to detect COVID-19 at targeted ports-of-entry could play a role in helping get the travel industry back up and running more safely, and give confidence to travellers. Would you rather have to queue for an invasive test which requires you to give a sample, or simply walk past a well-behaved sniffer dog when you disembark while they rapidly and discreetly screen you for COVID?

Our mathematical modelling work showed that, if enough dogs can be scaled up and deployed, dog screening in airports plus a confirmatory PCR test for those who are identified as positive by the dogs, could prevent more onward transmission than isolating symptomatic individuals only, or testing people with a LFT followed by a PCR test.

But airports are not the only place these dogs could have an impact. These dogs have the potential to be used to rapidly screen individuals at mass gatherings, such as sporting events, other travel hubs such as train stations, and perhaps even some work places.

We now plan to move on to the next phase of the trial and put this into practice, testing the ability of the dogs to detect infected individuals in public spaces, even if they’re asymptomatic.

As our success continues, my hope is that the incredible abilities of dogs to detect COVID-19 and other diseases could play a vital role in helping us to regain some level of normality and save lives.

I know you might be thinking, but we have vaccines now – why would we need dogs?

Vaccine rollouts are an incredible leap towards controlling the pandemic, but new variants will continue to pose a threat. It is likely that testing will continue to play a role for some time to come.  We will need to learn to live with this disease, and these dogs could help, not only to tackle COVID-19 here in the UK but in countries around the world. I hope they will play an important role in our readiness and preparedness plans to respond to new disease threats in the future.

Publication

James G Logan, Claire Guest, Sarah Y Dewhirst, Steven W Lindsay, Anna Last, Josephine E A Parker, Immo Kleinschmidt, John Bradley, John Pickett, Ann Rooney, Luke Cottis, David J Allen, Vanessa Chen-Hussey, Steve Morant, Erin Foley, Chelci Squires, Unnati Chabildas, Manil Shah, Courtenay K Greaves, Jessica Dennehy, Salvador Gezan, Sophie Aziz, Mark Somerville, Samuel Clifford, Billy J Quilty, Tim Gibson, Oliver Baerenbold, Sébastien Lambert, Martin Walker, on behalf of COVID Dogs Research Team. Using trained dogs and organic semi-conducting sensors to identify asymptomatic and mild SARS-CoV-2 infections. Pre-print.