Some people are more likely to infect others with coronavirus because they are prone to milder symptoms
Until recently, few people had heard the term super-spreader, but last week it became part of our daily language.
This largely began with Steve Walsh, a Scout leader in Hove, who found unwelcome fame when he was mentioned as a “super-spreader” of the new strain of coronavirus.
The term is used to describe those who transmit a disease to a larger number of people than others. They can show no symptoms and some secrete more of the virus than others.
Recent studies from China have shown that people infected with coronavirus – now officially called COVID-19 – usually only pass the virus on to two or three people (2.6 on average).
Steve Walsh (photo), a Scout leader in Hove, who found unwelcome fame when he was named a “super-spreader” of the new strain of coronavirus
Steve Walsh unknowingly infected at least 11 people during a skiing holiday in the French Alps. They include five cases in England, five people in France and one in Spain. Now home from the hospital, he has recovered and is no longer contagious.
But he is not the only super spreader. In Wuhan, China, where the virus originated, an infected person – who had none of the flu-like symptoms associated with corona virus, such as fever or cough – infected ten medical staff and four patients in one ward, according to a report published in the JAMA magazine earlier this month.
Super-spreaders are not limited to the coronavirus outbreak. During the 2003 SARS epidemic, most of the 204 cases in Singapore were due to only five super-spreaders.
In Finland, doctors discovered that only one school pupil infected 22 others with measles in 1998, although nine had been vaccinated. And in 1995 two people reportedly infected 50 others with Ebola in the Democratic Republic of Congo.
Super-spreaders are not limited to the coronavirus outbreak. Pictured: a woman seen in the London metro with a protective mask on
It has long been accepted that there is something called the 80/80 rule – 20 percent of infected people are responsible for 80 percent of broadcasts – Bill Keevil, a professor of environmental health care at the University of Southampton, Good said Health.
This is because some people shed larger amounts of virus particles than others when they cough or sneeze, which increases the chance that they will infect others. For example, children are more susceptible to the flu virus and shed longer than adults.
“We are aware that with every infectious disease, there are people who spread the disease more often than others,” Professor Paul Cosford, emeritus medical director for Public Health England, told Radio 4 today.
“It has nothing to do with their behavior; it’s just a biological fact, “he added.
People can become contagious before they develop symptoms because they already shed the virus in their saliva or feces
But there are reasons why some people become super-spreaders and others don’t.
“These people are more likely to have mild or no symptoms of the virus, so they have no indication that they are sick,” says Professor Keevil.
What’s in a name?
The diseases named after people. This week: Bell’s parese
The Scottish surgeon and anatomist Sir Charles Bell gave the first clear explanation for this facial paralysis in 1821.
Sir Charles has determined that symptoms occur when a certain facial nerve is compressed, causing the eyelid and corner of the mouth to hang.
The diseases named after people. This week: Bell’s parese (file image)
The cause is unknown, but is more common in pregnant women and those who have recently had a respiratory infection.
Treatment – usually a short course of oral steroids – must begin within 72 hours before the patient sees the most benefit.
About 70 percent of those with Bell’s paresis fully recover, which can take up to nine months. Some are left with long-term nerve damage, which may require surgery or Botox injections.
“This may have something to do with their immune system, which is less responsive to the virus – often symptoms such as fever are due to the immune response, the way the body kills a virus – but we don’t know exactly why. ‘Unfortunately, because they may not know that they are sick, they cannot take steps to isolate themselves.
People can become contagious before they develop symptoms because they already shed the virus in their saliva or feces.
In the case of the flu, for example, people may be contagious for a day before symptoms begin, making a super-spreader-led outbreak more likely.
But with coronavirus it is not yet known at what time people can pass on the infection.
“We do know that people are most likely contagious if they already have symptoms, but we are also aware that there is a possibility that some transmission may take place before that time,” says Professor Cosford.
For example, Steve Walsh returned with more than 100 other passengers on a flight from Geneva from the Alps, spent a night at his local pub, and went to a yoga class before feeling unwell and going to A&E.
An infamous super-spreader in the early 1900’s was Mary Mallon – also known as Typhoid Mary – who showed no symptoms of the disease she passed on to at least 51 people in the US.
In fact, she remained fit and healthy throughout her life, but was discovered as the common link in various outbreaks of deadly typhus. She was eventually quarantined against her will from 1915 until she died in 1938.
An autopsy showed that she had shed salmonella typhi bacteria – responsible for typhoid fever – from her gallstones, which disappeared from her body in faeces, without causing her symptoms.
John Oxford, professor of virology at Queen Mary University in London, points out that Typhoid Mary was able to spread infections far and wide because of her work.
“She worked in kitchens to prepare food, so it was much easier for her to infect her employers and people who eat in homes where they worked,” he says. “The bacteria has probably spread from her hands to surfaces and food.”
But there is a large group of individuals who almost always fall in the super spreader camp – and they are children.
A study published in the May 2016 issue of The Pediatric Infectious Disease Journal, comparing the rate at which children and adults reject the flu virus, found that children reject it earlier than adults, and longer.
“Children have no social distance and less trouble sharing personal space, which is why they easily pass on infections,” explains Professor Oxford. “And they constantly touch each other.”
Good hygiene is of the utmost importance to minimize the risk of catching coronavirus. It is a tough virus that lives much longer than the flu virus, which usually only survives 24 hours on hard surfaces.
“My own research has shown that coronavirus can survive up to five days on worksheets,” says Professor Keevil.
“You can pick up this virus by making contact with contaminated surfaces such as door handles, stair rails and table tops and then simply touching your mouth, nose or eyes [the virus can enter through the upper respiratory tract via the tear ducts] with your hands. People usually do this 15 to 30 times per hour.
“The most important thing is to take standard hygienic precautions, such as hand washing and regularly disinfecting surfaces, and to ensure that spread is kept to a minimum.”
Professor Oxford has more radical advice: “Temporarily dropping the habit of shaking hands can also make a big difference to the potential spread – I have that.”
Poor, good, best: how to get the most out of food choices. This week: Cream cheese
The combination of full cream cheese with sugar, cream and a cookie base yields more than 300 calories in just a small portion. It also contains 10 g of cholesterol-raising saturated fat and at least 4 teaspoons of added sugar.
The combination of full cream cheese with sugar, cream and a cookie base yields more than 300 calories in just a small portion. Shown: baked cheesecake (file image)
Good: Macaroni cheese
Made with lean garlic and herb cream cheese and Dijon mustard, a serving of 430 calories, with 6 g of saturated fat, compared to more than 700 calories and 20 g of saturated fat in a typical recipe.
Macaroni cheese: made with low-fat garlic and herb cream cheese and Dijon mustard, provides a serving of 430 calories (file image)
Best: Mackerel Pie
Prepare a nutritious 350-calorie lunch for two by mixing a pack of 180 g of smoked mackerel with 100 g of low-fat soft cheese and add the zest and juice of a lemon. A serving contains 240 mg of calcium and 7.4 mcg of vitamin D.
Mackerel pie: prepare a nutritious lunch of 350 calories for two by mixing a 180 g packet of smoked mackerel with 100 g soft cheese with reduced fat content (file image)