Vapers infected with Covid are up to 17 per cent more likely to spread it because they blow the viruses around when they breathe out, a study has claimed.
Experts say puffing out vapour from e-cigarettes could propel thousands of viruses towards people in the surrounding area.
And the Covid-plagued droplets could travel more than two metres, the outer limit of the UK’s social distancing rules, which endorse a ‘one metre plus’ approach.
Experts have called on vapers not to use their devices while in queues, at bus stops or other places where people are at risk of encountering a ‘vape cloud’.
In the study the researchers, from Mexico, Italy and New Zealand, said it would be ‘extremely intrusive’ to tell people to stop vaping indoors at home but that it might be sensible to ban it in public spaces such as restaurants and train stations.
They said the risk posed by ‘low intensity’ vaping, which was just exhaling gently, was smaller than the risk from speaking or coughing while close to someone.
The team did not compare vaping to smoking real cigarettes but said ‘most of the results we obtain are applicable to “mainstream” smoke exhalations emitted by smokers’.
Vapers infected with coronavirus are up to 17 per cent more likely to spread the virus, a study has claimed (stock picture)
In the study scientists modelled how much virus could be carried by low intensity vape clouds, when it is held in the mouth and pushed into the lungs before being exhaled, and high intensity, when it is inhaled directly into the lungs and blown out.
They found low intensity puffs from infected individuals led to a ‘miniscule extra contagion risk’, raising the chance of bystanders catching the virus by one per cent.
But high intensity jets of air, caused by someone actively blowing out the vapour, pushed up their risk by between five and 17 per cent.
Their model was based on a mechanical jet which produced a puff of air intended to be similar to that breathed out by vapers.
And to work out the difference in risk of transmission between different types of breathing, they considered the volume of air and droplets in each breath, the distance the air could travel and the possible viral load – number of viruses – that might be carried on it if they were infected.
The coronavirus is known to spread through the air when people breathe out, talk, cough or sneeze, and the more air that is expelled, the higher the risk is.
The researchers found that the breath volume and distance travelled was higher than normal breathing for people who vaped ‘intensively’.
This meant that, if they were infected with the coronavirus, more of these viruses could piggyback on the droplets in their breath and spread to other people.
They then applied this to a mathematical model to calculate the 17 per cent increase in risk, rather than measuring raw numbers of viruses or infections.
The scientists, led by Dr Roberto Sussman from the Universidad Nacional Autonoma de Mexico, said the chemicals in the vapour were unlikely to kill off the virus.
Although there was no proof that vapers were spreading the virus, they said: ‘While there is currently no factual evidence that pathogens have been spread through this route, it is entirely plausible that this should occur.’
They compared how much different activities changed the risk of someone passing on the coronavirus if they were infected with it.
Using a baseline of just normal breathing, they said ‘high intensity’ vaping raised the chance by between five and 17 per cent.
This risk increase was lower than if someone was speaking or coughing, they said.
Speaking raised the risk by between 40 and 80 per cent, while coughing more than tripled the chance someone would pass the virus on, raising it by 260 per cent.
The study was published as a pre-print on MedRxiv, and has not been peer-reviewed by scientists. This means the data has not been scrutinised.
Experts say Covid-19 is mostly spread through tiny infected droplets emitted into the air while someone is talking, coughing or sneezing.
They say it is unlikely infections are triggered after touching a surface that had previously been touched by someone suffering from the virus.
A study published last week found the risk of catching the virus from frequently touched surfaces including ATMs, petrol pumps and pedestrian crossings was low.
The team leading the study on vaping was based at universities in Italy, Mexico and New Zealand.
Professor Linda Bauld, a public health expert at the University of Edinburgh, told The Telegraph vapers shouldn’t use their devices while waiting in queues, at bus stops or other places where people are at risk of encountering a ‘vape cloud’.