© Justin Tallis/AFPJoggers maintain a social distance from each other on Clapham Common in London - Justin Tallis/AFP
Joggers should wear a face mask to prevent the spread of coronavirus, a University of Oxford expert has said.
Trish Greenhalgh, a primary health care academic, urged people exercising outdoors to cover their nose and mouth so they do not unintentionally transmit the disease.
Advice from the NHS encourages outdoor exercise during lockdown because of its physical and mental health benefits, but Prof Greenhalgh said joggers must also consider potential risks to others.
"There is no doubt the virus is in the air, there is no doubt that you can catch it if you inhale, and that someone else has exhaled," she told ITV's Good Morning Britain.
"The exercising jogger - the puffing and panting jogger - you can feel their breath come and you can sometimes actually feel yourself inhale it, so there's no doubt that there is a danger there."
Around two in five coronavirus infections are caught from people who do not have symptoms, she added, meaning that joggers and cyclists should take extra measures as a result.
A study co-authored by the professor which appeared in the British Medical Journal last year recommended additional social distancing precautions during exercise, because joggers' heavy breathing can produce "violent exhalations"
However the study acknowledged research from Japan which suggested that coronavirus transmission is as many as 19 times lower in outdoor settings than indoors.
Devi Sridhar, a public health professor at Edinburgh University, encouraged people to "take off your mask and run freely" when they are in open spaces, but to wear masks in busy areas.
The risk of coronavirus spreading as a result of exercise depends largely on how close someone is to another person and how heavily they are breathing, Prof Sridhar said.
The current World Health Organisation guidance says people do not need to wear masks while they exercise, as this may restrict their ability to breathe comfortably.
In January, a Government advert that said joggers were "highly likely" to have coronavirus was discontinued after regulators said there was no evidence to support its message.
The Cabinet Office agreed not to repeat the claim after it was contacted by the Advertising Standards Authority.
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