Professor Stuart Tangye is Leader of the Immunity & Inflammation Theme and Head of the Immunology & Immunodeficiency Lab at the Garvan Institute of Medical research. He is also a Professor (Conjoint) at St Vincent’s Clinical School, Faculty of Medicine, UNSW Sydney

Are children likely to be major spreaders of this virus, as is the case with flu?

Very possibly.

Children and young people can certainly be infected. Data from South Korea showed that 5% of SARS CoV2+ individuals were aged 10-19 years – this is 5x higher than this age group in China. More concerning tho was the finding that ~30% of SARS CoV2+ individuals in the South Korea cohort were aged 20-29 years.

We know that mortality for infected individuals in this age range is very low.

0-9 years – no known fatalities
10-19 yrs –  death rate 0.2%
20-29 yrs –  death rate 0.2%

Of the current 448 cases in Australia, 19 have been detected in individuals under 19 years of age ie. <5%. This increases to be ~10% for each increasing decade til it declines for >70 years.

Which means there are likely to be many asymptomatic (ie. apparently heathy) young people in the community who are infected with SARS CoV2; they are not infectious but as they are not showing any symptoms they are probably not self-isolating.

Are people who are infected but not showing symptoms likely to be major spreaders of this virus?

Again, this is a very real possibility. If young people are not self-isolating and are eg. going out to crowded bars or other places to socialise.

How long after symptom onset are you infectious?

This table indicates the incubation time is 4-14 days.


A recent study in the New England Journal of Medicine and Nature Medicine studied paediatric cases of COVID19; one finding was that SARS CoV2 was detectable in rectal swabs after they became undetectable in throat swabs ie. 4 weeks vs 2 weeks suggesting viral excretion can occur via the gastrointestinal as well as the respiratory tracts, with this being longer via gastrointestinal secretions.

How long does COVID-19 survive on surfaces?

One recent study suggested this varies depending on the type of surface ie. less stable on copper surfaces (<8 hours) but persists longer on cardboard and steel (~24 hours) and even longer on plastic (2-3 days).


Professor Allen Cheng, Professor of Infectious Diseases Epidemiology in the School of Public Health and Preventive Medicine at Monash University, has answered the following questions:

Can we please have some commentary on herd immunity + the coronavirus? It’s a big issue in the UK and elsewhere.

“It (herd Immunity) is a risky strategy, but may very well be the ultimate outcome. It’s hard to get enough situational awareness to know when things might need to be tightened up, we don’t know the duration of immunity after infection, the intensity of transmission in children isn’t clear, and it would be hard to prevent mixing between less susceptible and more susceptible groups. Public health interventions are a very blunt tool – it’s hard to work out how effective they are, and can’t easily be turned on or off.”

Is the 1.5 metres for social distancing accurate? Is there any scientific basis for it?

“The 1.5m level clearly isn’t a sharp demarcation (you’re not safe at 1.51m and at risk at 1.49m!), and some more recent studies have suggested that most droplets do fall mostly within 1m, so the 1.5 recommendation allows for some uncertainty. Here’s a paper that looks at droplet spread with coughing: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0050845


Professor Bruce Thompson, Dean of Health at Swinburne University, has answered the following questions: 

Does surviving Covid-19 give you immune protection?

“Yes it does. We are still not entirely clear whether it is full protection however it is much better than no protection.”

Does one need to experience at least lower respiratory symptoms like bronchitis to mount a protective antibody response needed for immunity? If the virus stays in the nose, would it only illicit a mucosal response and no humoral response?

“No that is not the case. Some people with the virus have not discernible symptoms at all, and the body still forms an immune response.”

Could this be a factor influencing why kids are under-represented among more severe Covid-19 cases? (are their snotty noses protecting them?)

“No that is not the case. The reason why children and younger people overall have not been as affected is that they are in usual health and well with an immune system that is working as it should. People with comorbidities such as asthma, emphysema, bronchitis, diabetes, heart disease are at higher risk irrespective of age. As we get older, as with everything else, our immune system gets tired as well.”

Can we please have some commentary on herd immunity + the coronavirus? It’s a big issue in the UK and elsewhere.

“The Herd Immunity concept works on the principle that if I am vaccinated or already had the virus I am protected from it, but more importantly I cannot give it some else. Furthermore if you have say have 100 people, 1 has the virus and the other 99 people have either been vaccinated or indeed had the virus, there is no where the virus can go –  ie it can’t be transmitted so it eventually dies out. So it comes down to statistics. If 1 person has the virus and the other 99 are not vaccinated or have it, the virus will spread easily. The more people that are vaccinated the better, as it makes it harder for the virus to spread. So the UK saying let the virus spread and all will be fine, as it will eventually build up a herd immunity. That would be fine if there was no risk to having the virus. However we know that the mortality is ~1-3% which in a population of the size of the UK could mean hundreds of thousands of deaths and millions hospitalised. This is not the correct approach to take.”

Image courtesy Paul Sableman (FL).

Should healthy people wear a mask? It’s also a big concern from the Chinese communities in Australia, who are angry at the advice from Australia health authorities saying ‘If you are well, you do not need to wear a surgical mask. There is little evidence that widespread use of surgical masks in healthy people prevents transmission in public.’

“The advice from the Australian Department of Health and Chief Medical Officer is correct. As panic buying of masks is stopping supply to the hospitals which really do need them.”

But a study in The Lancet finds wearing masks is effective in a hospital setting during SARS.

“Yes in a hospital setting where you know that the person has the virus.”

Should we be reconsidering the role of masks given that an “absence of evidence of effectiveness should not be equated to evidence of ineffectiveness”?

“We know they are effective on an individual basis if the person in front you has the virus and yes I take the point that no evidence is indeed evidence however from my previous point we don’t have the supply chain for everyone to have them and the hospitals need them.”

What is flattening the curve and why is it important?

“The flattening of the curve is in relation to the number of people who have the virus. Basically we are trying to stop the increase, or rise, in the number of new cases so if you imagine the curve of number of cases versus time, if there are no new cases the curve flattens out. The reason why it is some important is that we are demonstrating that the control measures are working and the virus is not being spread and hopefully eventually dies out.”

What is the best ways for individuals to do this / what are the best ways for communities to do this?

“The best thing to do is the simple things like hand washing and hand sanitising. Social distancing. If you are sick then isolate  – staying at home is perfectly fine. Keep a distance from each other. It is very similar to having a horrible cold. If you have a horrible cold you don’t want to give it to anyone and if you know someone with a horrible cold you normally don’t want to catch it, so you distance yourself. Don’t shake hands or kiss each other etc.”

What is the current situation like for the healthcare system and will it hold up?

“At this stage all is OK, however if the virus spreads as it has done in other countries like China and Italy it will put huge pressure on the health care system. This the very thing that we are trying to avoid by placing the country into isolation. It is also bigger than COVID-19 as taking up hospital beds with COVID-19 is displacing people with the usual things people go to hospital for. Plus we are about to enter influenza season which 300,000 people had in Australia and which killed ~800 people.”

Why Australia hasn’t moved to general school closures?  Do epidemiologists agree that children continuing to go to school minimises the risk to vulnerable groups such as the elderly?

“This is an interesting argument. Understandably we need to protect the most vulnerable which are the elderly and people with comorbities. So increasing their exposure is not a great idea. So if the government does close schools, which on one level makes sense, then children need to be looked after by a low risk group.”

Is Australia heading for the same situation as Italy? What’s the modelling?

“Hopefully not! And is the very reason the government is correctly following the advice of the CMO and putting into place the current measures. The sooner we do this, the quicker we can stop the spread of the virus. We know from countries such as Singapore etc that have putting in isolation measures they have effectively stopped the increase in cases. Countries that didn’t do this such as Italy etc have struggled to contain the virus.”

What works to contain the spread? Any data/research on that would be very valuable.

“The basic stuff. Hand washing, hand washing and hand washing! Social isolation.”

Why does it take a long time to build a vaccine?

“A vaccine is like a medicine. First it needs to be developed. For any medicine to be sold it needs to go through the standard process of clinical trials including phase 1 – 3 trials. We need to insure that the medicine is safe, will not do harm, and know how effective it is.”

How would a coronavirus vaccine work?

“Same is an influenza vaccine.”

How would a coronavirus vaccine be deployed?

“Same as the influenza vaccine.”

Are there examples of other coronavirus vaccines we can look to/studies showing SARS/MERS safety/efficacy?

“Yes they do help point us in the right direction.”


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