Silent spreaders with no symptoms accelerate coronavirus pandemic

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People not displaying symptoms could be a major driver of the spread of coronavirus.

A study published in the journal Science found that before China’s lockdown on 23 January, nine out of 10 cases of the pandemic were passed on by people who showed no symptoms of the illness.

The study’s lead, Columbia University infectious diseases researcher Dr Jeffrey Shaman, says these “stealth transmissions” accelerate the spread of the disease and help explain why it is more difficult to combat than previous viral outbreaks such as SARS.

A Lancet study of transmissions in Hong Kong suggested that the virus can be transmitted easily, even when symptoms are relatively mild. This could account for the fast-spreading nature of this epidemic, the study found.

Another study, examining 91 cases in Singapore, found that 48 per cent of patients caught the virus from people showing mild or no symptoms.

And The New York Times has reported that the United States Centres for Disease Control and Prevention believes up to 25 per cent of people infected in the pandemic may not show symptoms.

This is important because carriers are believed to most contagious about one to three days before they begin to show symptoms. 

Dr Shaman says people with mild infections are taking the virus into the community and spreading it far and wide.

He is not alone.

“People think, ‘If I don’t feel bad, I don’t have it and can’t give it to anyone’, and that is now misguided thinking,” Chad Petit, PhD, told

Chad Petit, an assistant professor in the department of biochemistry and molecular genetics at the University of Alabama at Birmingham School of Medicine, says the onset of symptoms is often delayed.

“The virus is propagating in your body, but your immune system has not recognised that something is going on systemically,” says Prof. Petit. “That’s why you don’t get a fever right away. Just because you don’t have symptoms doesn’t mean you don’t have the virus.”

Unwitting carriers – becoming known as ‘silent spreaders’ – are rarely truly asymptomatic. They are likely to eventually feel the effects of the illness.

If carriers can transmit the virus to others, even when feeling healthy, keeping only sick people in isolation will not halt the contagion.

So, what should we do?

ProPublica’s Caroline Chen says increased testing is vital because it can let people know if they’re sick before symptoms emerge and prompt them to self-isolate.

“At a big picture level, testing helps public health officials know where the disease is spreading and better allow them to direct resources and response efforts.”

New York Times medical correspondent Apoorva Mandavilli concluded that social distancing is still the key policy.

“Rapid tests for infection might help detect people, especially healthcare workers, who are infected yet feel normal. Masks may help. But experts kept returning to social distancing as the single best tool for stopping the chain of transmission in the long term – not lockdowns, necessarily, but cancelling mass events, working from home when possible and closing schools.”

Jeremy Howard, research scientist at the University of San Francisco, believes getting as many people as possible to wear masks is vital.

“You might walk into stores over the next few days and sicken dozens without knowing it. Some might die. Others will think they are dying before they recover,” he wrote in The Guardian.

“Almost any kind of simple cloth covering over your mouth, such as a homemade mask, or even a bandanna, can stop the (COVID-19) assassin in its tracks.”

There is debate about the effectiveness of many masks as a protective device, and a need to prioritise appropriate protective gear for front-line medical workers.

But Jeremy Howard’s rallying cry is emblematic of the coronavirus crisis. It is aimed at helping those who are unaware they have the virus from spreading it.

We must think about others as much as ourselves.

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Total Comments: 22
  1. 0

    I watched a video this morning the takeaway line being ‘My mask protects you, your mask protects me.’ Even home made masks are worthwhile. Leave the PPE to the front line workers definitely, but we all need to be encouraged to use other types of masks in addition to social distancing and hygiene.

  2. 0

    I agree, it’s the old saying better to be safe than sorry. Stop thinking of just yourself but the other people you may inadvertently come into contact with.

  3. 0

    A homemade mask is easy to make from material at home and for us ordinary people works well.

    • 0

      What if you don’t sew? I’ve never been a great fan. I don’t have material, nor a sewing machine. The only thread I have is for mending, and it’s only a basic kit.

    • 0

      One thing about a home made cloth mask is that if you rinse it in an Alkali solution, (I use borax as it has no external effects, does not pass through the skin, and even if swallowed is slightly less poisonous than table salt. – dissolve borax powder in water until there is a bit of undissolved powder on the bottom of your container,- then the water is saturated with the borax, let the mask you have rinsed in the borax dry, then the borax is still in the cloth, so if you have a high dose of droplets, they will almost all be killed, as the droplet will combine with the borax all through the cloth, and immediately the virus environment is deadly for viruses whereas masks without Borax can keep the virus alive to work it’s way through the mask and then into you, – the last thing you want!
      Wipes and cleaners using 70/80% alcohol are useless in a mask, as it evaporates immediately and would knock you out anyway, – and like wise using borax as a wipe fluid, – the water evaporates like the alcohol does, but the Borax remains at full strength (until some one wipes it off of course but even then the borax will kill the virus on that persons, – finger or whatever.
      Borax is widely available at smaller supermarkets, chemists and agriculture suppliers, and is very inexpensive, – it also makes your mask fire-proof 🙂 (actually quite a helpful quality for smokers using masks, and probably smokers need to be wearing masks more than most people).
      PS, Borax will dissolve more in hot water but then precipitates out as the water cools so you need to mix the borax with water at room temperature, or not much more.

  4. 0

    A homemade mask is easy to make from material at home and for us ordinary people works well.

  5. 0

    I agree with all comments I use my motorbike bandanna and my whipper snipper face mask I looked in the mirror and gave myself a fright but I am safe , I hope !!

  6. 0

    Those who publicly advocated against the wearing of masks may well have something to answer for. I believe they did this so that the public would not take N95’s needed for medical professionals. However, if droplets can’t get out of a mask, droplets will have difficulty getting in. But just wait, as usual people in charge shut the gate after the horse bolts. Basic disposable masks are available online. Everyone should be required to wear a mask when they leave the house. No exceptions. Easy to make and if you can’t make one there’s always going to be a good Samaritan who will. Make a mask project groups are springing up in various towns. They are made from washable cloth with a pocket that holds a folded piece of paper towel. By initially insisting public masks are ineffective, they’ve probably caused this hideous disease to spread more widely.

    • 0

      I was just a bit worried about wearing a mask, Brissiegirl. If someone sneezes or coughs and wet droplets land on your mask, does that mean you’re breathing in those contaminated wet patches into your lungs?

    • 0

      Brissiegirl I’m afraid you are quite mistaken.

      Most masks you see people wearing offer virtually no protection from infection at all. They are so badly fitting even those who are sick and coughing will still spread the droplets.

      For the general population, wearing a mask when you are actually sick and coughing may help protect other people from you. However, if you are healthy they offer almost no protection from infection.

      Further, these masks are meant to be worn for a maximum time frame of 20 minutes then disposed of. They should not be reused. I suggest the public are certainly not doing this.

      By far the main infection route is by people picking up droplets from surfaces and transfering them to their eyes, nose and mouth. This is the reason why we are being asked to wash hands properly and keep hands away from our faces.

      Also reconsider the use of disposable gloves. They offer absolutely no protection at all and are an unnecessary expense. The virus does not infect through absorbtion through the skin! It is directly transmitted from the hands. Wearing gloves and touching contaminated surfaces then your face is not affected by wearing gloves.

      Wear a mask if it gives you confidence, but do not think for one minute it offers a whole heap of protection. A single scratch or rub of the eye with a contaminated finger can still infect you, mask or no mask!

    • 0

      I believe you are correct, Brissiegirl, these sorts of generalised announcements are designed to be vaguely generally understandable and with no understanding, – or ignoring, that the devil is in the detail..
      They are designed to calm everyone down but they don’t understand that most of us are clever enough to see the holes in their logic, so actually get more concerned.

      EG, – Although people can put on a mask so it is not very effective, – with a bit of help or just observation of the airflow into your nose, it will be more effective next time and almost completely effective the third time.
      So those general announcements are only for the completely dumb, and the problem is the difference between 80% successful Lock Down and 70% Lock down is that with 70% we still are in a losing situation, – it still gets all of us.

      If your mask is on properly, and, as I have said above, using Borax as a good medium, even better, soaked with dried alakaline solution, it can tip that 70% back into the 80 or even 90% effective, – the Coronavirus starves to death, RIP.

      Just how longer a borax soaked mask lasts than an alkali Neutral mask lasts, nobody seems to have done that test, – I would think that the dissolved borax and dead virus would cause a mini wet patch so new air would go around that spot, but at least you can re-use your mask with no fear at all, – it is almost impossible for a virus to live in a strongly alkaline environment, – sort of like rabbits being immune to the direct hit of a modern rifle bullet through the heart.
      and KSS, if your washing solution is borax, it will considerably reduce the possibilty of someone touching that button before you leaving any living virus for you to rub on your face, and if you have the borax solution on your face it would kill the virus anyway. – not suggesting we should all start rubbing our faces, but one should consider that washing your hands in Soapy water is mandatory, – soap is about max 80% alkaline, that is why it works.
      I have the probem that when I have to enter a situation they require me to wash off my 100% borax solution on my hands that will stay for a long time, and replace it with 80% soap solution that will disappear more quickly.. – You can’t win them all!

  7. 0

    Finally they are admitting that face masks are effective, someone forgot to send the memo to our politicians and chief medical officers! Has anyone looked at the covid-19 timeline in Australia recently, looking back we could have stopped it numerous times and we would not not have to be so restricted in our movements. The kids are getting restless that is for sure, how long before parents start going mad too?

    • 0

      Most of the cases came off cruise ships. Spread in the community without direct contact has not been great, so far. It is going to spread faster if irresponsible people are not isolating themselves as directed. Since some unthinking members of the population cannot be trusted to obey the law they spoil things for everyone.
      Simply putting on a mask isn’t going to save anyone unless it is made of suitable material and washed every time they take it off since it could be contaminated.

    • 0

      Where did you get your medical degree Incognito?

    • 0

      Very funny KSS, having a go at my opinions again. Don’t know what that has got to do with my comment anyway. I read from several doctors websites they have a degree, and I weigh up what I believe in, not just what mainstream media keeps on telling us.

  8. 0

    Hi KSS don’t forget to tell all the doctors and medical staff their mask is useless. Good job you don’t live in China otherwise you would surely be in jail.

    • 0

      Where does KSS say that that the masks doctors are wearing are useless? If that were the case a great many of them would be sick or dead by now.
      They wear very different masks. Just watch TV and sooner or later you will see for yourself.
      Or Google a pic.

  9. 0

    Thank you for printing this article. I am so relieved to know the people who have written to this forum are not listening to the fools that are telling us masks are useless. There will be a u-turn soon after the government officials realise THEY ARE NECESSARY! to prevent the spread of the covid19. For a more detailed explanation about the need for masks check out the information on The comment “My mask protects you, Your mask protects me” is good advise. Keep safe all of you!.

    • 0

      The only mask I would consider is the surgical mask for which you can find a pattern online.
      Many groups in America are making these for hospitals.
      However the best preventative is staying at home!

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