HEAVY breathers could be Covid superspreaders, scientists have warned.
And the culprits are typically those who are older and fatter.
Heavy breathers could be Covid superspreaders, scientists have warned. Pictured: A face covering sign in Stratford, LondonCredit: Rex Features
The coronavirus is spread through respiratory droplets from coughing and aerosol particles from breathing or talking.
A study in the US, led by Tulane University, measured the level of aerosols exhaled by 194 healthy people aged between 19 to 66 years old.
They found that as age and body mass (BMI) increased, so did the likelihood someone was a heavy breather.
Those with the highest BMI combined with age exhaled up to five times more particles per litre than those on the other end of the scale.
Researchers said 20 per cent of the participants with heavy breathing accounted for 80 per cent of the exhaled particles in the room.
By scientific definition, this would make them “superspreaders” in the role of disease transmission.
Superspreaders are a small group of people (20 per cent or so) who cause the majority (80 per cent) of new cases of disease.
Scientists have been debating what the characteristics of a superspreader are, and this study could give clues.
Young and healthy tend to generate far fewer droplets than the older and less healthy
Dr David Edwards
The study paper, published in the journal PNAS, said: “The phenomenon of superspreading of Covid-19 may be not only a matter of air currents and proximity of infected and naive hosts but also of phenotype.”
As age and body mass (BMI) increased, so did the likelihood someone was a heavy breather. This would make them a “superspreader”, because those with heavy breathing accounted for 80 per cent of aerosolsCredit: PNAS
The study did not assess directly assess how much coronavirus a person would spread via breathing and if this would cause someone else to become infected, as the participants did not have Covid.
But it did use monkeys purposely infected with the virus to get a better understanding.
The monkeys exhaled more aerosol droplets as their Covid disease progressed.
It reached a peak a week after being exposed to the virus, before falling to normal levels after two weeks.
The increase of aerosols also happened in monkeys without any symptoms.
Dr David Edwards, lead author and professor of the practice of biomedical engineering at Harvard University, said body composition variability between people plays a role in how the virus is spread.
But he said: “While our results show that the young and healthy tend to generate far fewer droplets than the older and less healthy, they also show that any of us, when infected by Covid-19, may be at risk of producing a large number of respiratory droplets.”
The World Health Organization (WHO) says aerosol transmission is more likely to happen in certain settings, mostly in crowded indoor places such as restaurants and offices.
But the main way the virus spreads is through respiratory droplets and close contact.
Maria Van Kerkhove, an infectious disease epidemiologist at the WHO, tweeted in October that “superspreading is a hallmark” of coronaviruses.
“Superspreading” can also be used to describe an event whereby coronavirus runs rife in a group of people.
A “superspreader event” is when a person with a higher ability to spread the disease causes a large number of cases in one go.
Benjamin Althouse, research scientist at the Institute for Disease Modeling, told AFP that the 20:80 rule may in fact be even more extreme, at 10:90.
He said this transmission pattern is like “throwing matches on a pile of kindling”.
“You throw one match, it doesn’t ignite. You throw another match, it doesn’t ignite. You throw yet another match, and this time you see flames blaze up.
“For SARS-CoV-2, this means that while it is difficult to establish in new places, once established, it can spread rapidly and far.”
Superspreader events such as church services, gym classes and choir practices have been at the root of case clusters, and in the early days of the pandemic, cruise ships were the perfect setting for these outbreaks.
The nature of coronavirus thriving in superspreading events means it could be a while before sporting events, weddings, concerts and music and religious festivals return.