StemCell Therapy

Why the two-metre rule may not be enough

SOCIAL distancing guidance is to keep two metres away from people we dont live with. This rule is thought to be based on experiments from the 1930s that suggested droplets released from coughs and sneezes can travel between one and two metres.

But this understanding may be outdated. In an experiment led by the Health and Safety Executive, a cough from a medical manikin called Violet provides a graphic illustration of just how easily and how far coronavirus particles can spread.

In the demonstration, Violet coughs up a liquid laced with a dye that shows up under ultraviolet light. The dye is meant to reveal how droplets containing coronavirus particles are propelled through the air when we cough.

"You see thousands of droplets coming out of Violets mouth, with some reaching the ceiling and the far wall, which is at least two metres away," says paediatrician Dr Guddi Singh.

"Some of these droplets land on my hand, even though I am not in the direct line of the cough. If these droplets contained the virus, I would be infected. It is incredibly contagious.

"The experiment shows me why we need social distancing of at least two metres," she says. "But even at that, you are just on the fringe of where the spread could be happening."

Indeed, new research published in the Journal of the American Medical Association suggests that two metres may not be nearly far enough; that coronavirus particles can be propelled up to eight metres by sneezes and six metres by coughs.

Some experts suggest that the larger droplets in saliva and mucus the ones believed to carry Covid-19 will fall safely to the ground within two metres. However, the US researchers said their experiment calls into question our understanding of what a safe distance might be.

Another report even suggests we may have more than coughs and sneezes to worry about. The prestigious National Academy of Sciences in the US recently warned that the virus may also be spread by the fine mist we produce when we talk and breathe.

One study suggests this can spread genetic material from the coronavirus more than two metres away from patients. This raises the possibility that the virus can linger in the air and potentially infect someone who walks by later.

All this research has prompted the World Health Organisation to start a review of its advice on the use of face masks.

Dilemma of the silent spreaders

THE spread of Covid-19 by people who arent showing symptoms is one of the reasons the virus is so dangerous. A study published in the journal Science concluded that 86 per cent of cases have either no symptoms or only very mild ones.

Countries such as Iceland and South Korea have reported a huge number of silent spreaders. In South Korea, 40.2 per cent of those aged 20 to 29 fell into this bracket.

It is not known why some people dont show symptoms, but it may be due to differences in their genetics.

How long does the virus survive?

WHETHER you have symptoms or not, the virus will be released from your respiratory system into the air and the droplets can "last for many hours on different surfaces which we may then touch", says Dr Singh.

"A recent study in the New England Journal of Medicine revealed the virus can survive suspended in the air for up to three hours. It can stay on cardboard for 24 hours and plastic for 72 hours."

This, says Dr Singh, could have implications for online shopping.

"In countries that seem to have managed the outbreak pretty well, such as Singapore and Taiwan, all deliveries are treated very seriously because it is clear that this could be another mode of transmission.

"With deliveries, there is advice that plastic items should be wiped down with soap and water."

Other experts say you are unlikely to reach every nook and cranny, so would be better off keeping your hands clean.

Its not just a cough and fever

THE official advice is that the two main symptoms of Covid-19 are a high temperature and a "new and continuous cough". Indeed, data gathered by the WHO in February on more than 55,000 confirmed cases in China showed a fever to be the most common symptom, occurring in 87.9 per cent of cases, followed by a dry cough (in 67.7 per cent).

Other symptoms listed included fatigue, coughing up phlegm, sore throats, headaches and diarrhoea and vomiting.

In the last ten days of the pandemic, a new symptom has emerged: loss of sense of smell. Data collated by ENT UK, which represents ear, nose and throat specialists, suggests this inability to smell and, often, to taste may be the very first sign.

Indeed, a new report from Kings College London points to it being one of the most common symptoms.

Younger people are at risk too

It is known that older people and those with underlying conditions such as type 2 diabetes and heart and lung diseases, such as chronic obstructive pulmonary disease (COPD), are more likely to become severely ill with coronavirus. A report in The Lancet last week where researchers from Imperial College London analysed data from China showed how the risks of serious illness and death rise sharply as we get older.

While a 20-year-old has about a 1 per cent chance of their illness being so severe that they are hospitalised, the risk rises to around 4 per cent for someone in their 40s; 8 per cent for someone in their 50s; and 19 per cent for the over-80s.

Yet, younger people are not invincible. Data from NHS England shows that while the vast majority of the almost 5,000 deaths in England have been in the over-60s, 396 younger people under 60 have lost their lives to Covid-19.

It is possible some peoples genetics makes them more vulnerable. Another theory revolves around the viral load the amount of virus someone is initially exposed to.

With some viruses, the more you breathe in, the sicker you get, which could explain why young nurses who are in close contact with lots of sick patients are dying from coronavirus.

The power of handwashing

In 2018, mathematician Dr Hannah Fry, who presents the BBC2 show with Dr van Tulleken, simulated a pandemic of a deadly flu virus. Her experiment revealed how quickly the contagion could be slowed simply by handwashing.

Washing hands an extra five-to-10 times a day would halve the number of people who caught the virus in the next 100 days, she says.

"The way that pandemics spread is all exponential, which means tiny things can have a massive impact. Things like handwashing, done properly, can genuinely make a difference," says Dr Fry.

:: Coronavirus, Horizon Special, BBC2, Thursday April 9, 9pm.

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Two metres may not be nearly enough: What scientists now know about the virus - The Irish News

This entry was posted on April 9, 2020 at 8:41 am and is filed under Genetic medicine. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. |