Singing or shouting when meeting friends and family could increase the risk of spreading coronavirus, one of Britain’s leading scientists has warned.
From Monday, groups of up to six people from different households are allowed to meet up, as long as they do so outdoors, and while retaining social distancing.
But Government scientific advisers have urged such groups to rein their excitement in - warning that raised voices may be more likely to allow the spread of Covid-19.
Professor Peter Openshaw, who sits on the the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) said there was little danger in meeting loved ones outdoors, if individuals kept two metres apart.
But he said singing or shouting could increase that risk.
Though the main form of transmission of Covid-19 is coughing and sneezing, it may also be spread by exhalations, which can allow droplets emit further, and encourage the production of more small particles, called aerosols.
Prof Openshaw said: “Essentially, if you're sitting in the open air at safe distance, not speaking close up to somebody - and particularly not shouting or singing loudly, then that seems to be very low risk.”
It follows a study by the London School of Hygiene & Tropical Medicine (LSHTM) which examined whether particular types of activities and events increased the spread of coronavirus.
Its researchers cited the example of a choir rehearsal in Washington which saw 87 per cent of singers infected.
Sebastian Funk, director of the LSHTM’s centre for the mathematical modelling of infectious diseases, said: “If you can identify certain types of activity — is it something about people breathing a different way, so spending two hours together playing violins is less risky than singing? — this has important implications for control strategy.”
A report by the US Centres for Disease Control and Prevention about the Skagit Valley Chorale ensemble in Washington state suggested singing might help spread the virus.
“The act of singing, itself, might have contributed to transmission through emission of aerosols, which is affected by loudness of vocalisation,” it said.
In most settings, droplets cannot travel further than six feet - which is less than two metres.
But last month William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, said that singing could allow droplets to spread further than this.
"These droplets are usually transmitted within three to six feet, but these droplets can be pushed farther out, sometimes even beyond six feet, if you give the exhalation more energy, with a cough or a sneeze or even singing," he said.