Simply breathing or talking may be the most common ways the coronavirus spreads, a study suggests.
Chinese scientists found Covid-19 patients exhale millions of viral particles per hour, even if they have mild or no symptoms.
They say it highlights the need for face masks, which Britons are only advised to wear when on public transport or in tightly-packed shops.
But they are not mandatory in Britain, unlike in other European countries such as Germany, the Czech Republic and Austria, which have all averted major crises.
Experts told MailOnline the evidence was now clear that mandatory mask wearing would ‘by far have the biggest impact’ in preventing the spread of coronavirus in the UK.
Like most respiratory illnesses, the highly-infectious disease is spread in tiny droplets of moisture that carry viral particles.
It was previously thought that the main source of transmission was via these droplets from coughs and sneezes.
But the latest finding suggests the coronavirus can spread just as easily in aerosols in the breath and may explain why it has managed to rapidly race around the world.
The researchers also found that toilets and floor surfaces were ‘reservoirs’ for the virus – but everyday items such as mobile phones were not.
Breathing may be the most common transmission route for Covi-19, Chinese scientists say as they reiterate the importance of face masks (file)
The study, not yet published in a scientific journal or scrutinised by other scientists, was led by the Center for Disease Control and Prevention in Beijing.
Thirty-five Covid-19 patients were recruited and nearly 300 viral samples were collected from their breath, on surfaces and in the air inside hospitals.
The study found, on average, there was three times the amount of virus in patients’ breath (16.7 per cent) compared to on surfaces (5.4 per cent).
The viral load in patients’ breath was also four times higher than in air samples (3.8 per cent) in their hospital rooms and corridors.
Commenting on the findings, Ian Jones, a virologist at the University of Reading, said the study was ‘very valid’.
WHAT IS THE UK’S FACE MASK POLICY?
The UK Government was one of the last in the world to start recommending face coverings.
It said there was no evidence they worked and was concerned the masks would give people false confidence.
Ministers U-turned in mid-May to say Britons should wear a face covering on public transport or in shops where social distancing is not always possible.
It added that homemade cloth face-coverings can help reduce the risk, but surgical masks or respirators should continue to be reserved for healthcare workers.
Ministers added that face coverings should not be used by children aged under two or those with respiratory conditions.
People who may find it difficult to manage the masks correctly such as primary age children unassisted are also advised not to wear them.
Officials said the guidance was being issued in response to there being ‘more movement outside people’s immediate household’ as Britons start returning to work.
He told MailOnline: ‘Aerosols are by far the biggest source of virus and blocking them, with a mask for example, will have by far the biggest impact.’
Contaminated surfaces were thought to be one of the main ways Covid-19 spreads, after a wealth of studies showed the virus could survive on metal and plastic for days.
England’s chief medical officer Professor Chris Whitty urged Britons in March to be wary when touching door handles or rails on buses and trains then touching their face.
But the Chinese study found just one handrail had detectable levels of the virus that could cause infection.
In the paper, the researchers – led by Professor Jianxin Ma, from the CDC in Beijing – said: ‘These observations do not support the widely-held belief that direct transmission by contact with surfaces plays a major role in Covid-19 spread.’
Among the five categories of surfaces, toilets had the highest SARS-CoV-2 – the official name of the coronavirus strain – positive rate at 16.7 per cent.
This was followed by hospital floors (12.5 per cent), patient touching surfaces such as bins, doors and handrails (4 per cent) and medical equipment (2.6 per cent).
Surprisingly, only two out of 22 surface swabs from the mobile phones of Covid-19 patients had detectable levels of the infection – despite the gadgets being known to harbour germs.
The researchers said the amount of the virus that patients exhale is influenced by the stage of their illness and possibly their age.
They found the SARS-CoV-2 breath emission rate was the highest within three days of showing symptoms, with patients breathing out an average of 105 viral particles per minute.
This finding was consistent with previous reports that showed viral load in throat swabs was highest at the time of symptom onset.
The researchers also suggest that over-50s exhale more of the virus into the atmosphere than younger patients, but they admit their sample size was too small to be certain.
Middle-aged and elderly people struggle to fight off the virus more than younger people.
It means the virus is able to fester and duplicate in their body more easily, increasing the amount of infection in their respiratory system.
Because they harbour more of the virus, it is thought that they also expel more of it when they breathe.
Writing in the study, the scientists said: ‘Large respiratory droplets and direct contact transmissions are presently cited as major transmission routes for the Covid-19.
‘In contrast, we show that the surfaces of mobile phones and various handles frequently used by Covid-19 patients presented very low probabilities of SARS-CoV-2 presence.
‘Evidences from our work show that exhaled breath emission may well be the most significant SARS-CoV-2 shedding mechanism, which could have contributed largely to the observed cluster infections and the ongoing pandemic.
‘Accordingly, measures such as enhanced ventilation and the use of face masks are essential to minimise the risk of infection by airborne SARS-CoV-2.’
It comes after a separate US study found talking in a confined space could spread coronavirus.
Researchers at the National Institutes of Health (NIH) found that droplets of spit that can contain infectious particles of coronavirus can linger in the air for eight to 14 minutes after someone speaks.
Especially concerning, even a person with no symptoms of coronavirus can leave a trail of coronavirus in the air after talking.