Why ‘true’ spread of COVID-19 must be revealed

Actuary and mathematics expert says his modelling shows there were about 20,000 carriers of COVID-19 in Australia in early April and not the 3000 active cases reported.

covid-19 modelling cases death rates infections

COVID-19 modelling completed for the Actuaries Institute suggests there were as many as 20,000 virus carriers in Australia at 9 April, far higher than 3000-plus active cases reported at the time.

The modelling also urges government and non-government working groups throughout the country to have a better understanding of the true spread of the disease, and the risks, before restrictions are relaxed.

In an article prepared for the Actuaries Institute's COVID-19 Working Group, Douglas Isles, an actuary with a Master of Arts in mathematics from Cambridge University, said modelling suggests that at 9 April there may have been around 20,000 carriers of COVID-19 in Australia, a much higher number than the 3000 or so active cases reported.

The modelling mirrors research by Dr Christian Bommer and Professor Sebastian Vollmer from Göttingen University in Germany. They used estimates of COVID-19 mortality and time until death, from a study published in The Lancet Infectious Diseases, to test the accuracy of official records and discovered, on average, that only about six per cent of coronavirus infections were being reported. The true number of infected people worldwide may have already reached several tens of millions, they estimated.

Mr Isles said a straightforward analysis of available data suggested that confirmed active cases in Australia are hugely under-reported.

“The focus in the media has been on three key data points around COVID-19: deaths, confirmed and active cases,” he said.

“We need to talk more about estimates and monitoring of community infection. Those risks need to be better understood before authorities decide when and how to relax current restrictions, an issue looming large for policymakers.

“Noting there are a lot more people with COVID-19 than there are confirmed cases, the public needs to be aware of the need for greater vigilance.”

Actuaries Institute chief executive Elayne Grace said the institute had established a working group to help advise its professional members, industry and policymakers seeking to understand the impact of the virus on our society and economy.

“We are looking at community health aspects, but also how the virus impacts business sectors as diverse as health, insurance and superannuation …

“The Actuaries Institute working group will also undertake assessments and approaches that can help governments and other groups manage Australia’s eventual end to this lockdown period and ensure the impacts are as limited as possible.”

Mr Isles said that while the modelling was simple, “the key point is that the reported data is an order of magnitude less than the actual data”.

He said his model was based on a number of authoritative sources including the Department of Health and the World Health Organisation (WHO).

Australian Department of Health data showed 330,000 people had been tested for COVID-19 at 9 April. At that time, there were 6103 confirmed cases, 51 deaths and 2987 recoveries.

The median age of death was 79, the median age of cases 47, and most cases were acquired overseas.

Mr Isles also used WHO data that tracked time lapses from the onset to recovery in various scenarios, including mild and severe cases. He said he used Australia-wide data covering 9 April statistics, plus rate of population testing, number of positive results and recovery and fatality rates.

He explained that using a constant carrier mortality rate and a constant time frame from infection to death allowed modellers to infer new carriers at a point in time. Applying a carrier mortality rate estimate of 0.5 per cent to the data on Australian COVID-19 deaths suggests there may have been around 400 new carriers per day in the week to 12 March, and 800 per day in the week to 19 March. This means it was likely that there were around 10,000 carriers by 19 March, and more than 20,000 carriers by 9 April.

“With access to more granular data, particularly around the demographics of those tested and the dynamics of viral transmission, these estimates could be improved,” he said.

“For COVID-19 we have a sample of 330,000 people tested, which is over one per cent of the population. It is reasonable for the public to expect to be provided with health experts' estimates of community infection rather than focusing purely on confirmed cases.”

The Actuaries Institute's COVID-19 Working Group involves a core group of 13 actuaries, supported by a further 50 actuaries working on a wide range of issues, advising business leaders, regulators and policymakers.

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    COMMENTS

    To make a comment, please register or login
    Tanker
    16th Apr 2020
    4:08pm
    Given the restricted nature of testing in Australia it would be reasonable to assume that the official figures underestimate the actual spread of the virus.
    JAID
    16th Apr 2020
    5:02pm
    That would be right and a point which those advising government would not be missing I think tanker. Without broad testing the present Deaths/Infected/Clear statistics are the most accurate they can go on but are clearly skewed to the obvious only. They say themselves that doing tests is critical. They do not have enough capacity for wide testing currently so have to do the next best thing, something necessary anyway; try to keep as many of us as possible in our own homes.

    I called the local testing operation with several of the symptoms before going to argue a traffic infringement in Court. They did not want to waste a testing kit on me (understandable in the circumstances) but the Court would not let me in.
    ozrog
    16th Apr 2020
    5:06pm
    We have the highest testing in the world and restrictions have been lifted. 45,000 tests available in SA over the next 2 weeks.
    Sundays
    16th Apr 2020
    6:49pm
    What restrictions have been lifted? Another 4 weeks minimum was announced by the PM today
    ozrog
    16th Apr 2020
    7:05pm
    Sundays restrictions for testing.
    Tanker
    16th Apr 2020
    4:08pm
    Given the restricted nature of testing in Australia it would be reasonable to assume that the official figures underestimate the actual spread of the virus.
    ozrog
    16th Apr 2020
    7:08pm
    restrictions for testing have been lifted. Sore throat or runny nose or cough orf ever or breathing problems. Now not combined but only 1 needed.
    Life experience
    16th Apr 2020
    4:27pm
    Test all patients coming into hospital and all medical staff to see if any carriers.
    There needs to be testing of people without symptoms.
    It could be random or to improve safety test all in hospitals.
    I know of 2 people who are positive without any symptoms at all. They are feeling great.
    panos
    16th Apr 2020
    4:31pm
    and I suppose they are quite happy walking around about everywhere.
    Jim
    16th Apr 2020
    4:34pm
    Just listened to the nightly review of the government response to this very question, the chief medical officer has dismissed these figures, he indicated that the numbers quoted by the government might not be correct, but the numbers quoted in this article are based on many unknowns and are highly unlikely to be accurate and only time will tell.
    Incognito
    16th Apr 2020
    8:51pm
    Yes I agree they might not be accurate and if they are then why are there not more people who are sick and dying?
    Farside
    17th Apr 2020
    3:06am
    it estimates 100 more deaths in the next three weeks based on the assumptions, how many more do you want?
    Incognito
    17th Apr 2020
    3:14am
    I don't want anymore and I do not think people will be dying from the virus but rather from their previous health issues and then it will be recorded as Covid-19.
    Macheke
    16th Apr 2020
    4:54pm
    I agree with Tanker that it is obvious that the infection numbers are greater as many people could have it with little or no symptoms or the symptoms are yet to manifest themselves. To my mind the issue is that a "one size fits all policy" may sound "fair" but it is not the way for Australia to combat the dual issue of economic damage and containing the virus. In simple terms there are at risk people (say over 50 and with health issues) and low risk people; the rest. We need to protect the "high risk" by minimising the chances they are infected. This means that they and the people that come into regular contact with them (eg age care workers) need to isolate themselves from the general population to extent possible. The rest should have fewer restrictions and, in particular, should be encouraged and assisted to work. Opening schools fits in with this. I have heard that the teacher's union has been opposed to schools opening as it puts their older members at risk. These members should not go to schools but can be used for online classes and other "work from home tasks". We need to start to balance the risks to the economy with the risk to loss of lives. Not easy but we need to have solutions that do not focus on the "one bad example". There was a good quote on 60 minutes when an expert said "if you want to save lives you need to have a speed limit of 5 kph.
    Incognito
    16th Apr 2020
    8:54pm
    Well said, we need to lift some restrictions and concentrate our resources on protecting the vulnerable not the whole population at the cost of the economy being destroyed any further. Workers and students need to go back to work and school, those who are older or immune compromised can choose to stay home.
    Macheke
    16th Apr 2020
    4:54pm
    I agree with Tanker that it is obvious that the infection numbers are greater as many people could have it with little or no symptoms or the symptoms are yet to manifest themselves. To my mind the issue is that a "one size fits all policy" may sound "fair" but it is not the way for Australia to combat the dual issue of economic damage and containing the virus. In simple terms there are at risk people (say over 50 and with health issues) and low risk people; the rest. We need to protect the "high risk" by minimising the chances they are infected. This means that they and the people that come into regular contact with them (eg age care workers) need to isolate themselves from the general population to extent possible. The rest should have fewer restrictions and, in particular, should be encouraged and assisted to work. Opening schools fits in with this. I have heard that the teacher's union has been opposed to schools opening as it puts their older members at risk. These members should not go to schools but can be used for online classes and other "work from home tasks". We need to start to balance the risks to the economy with the risk to loss of lives. Not easy but we need to have solutions that do not focus on the "one bad example". There was a good quote on 60 minutes when an expert said "if you want to save lives you need to have a speed limit of 5 kph.
    ozrog
    16th Apr 2020
    5:07pm
    I prefer to believe our CMO using Australian data.
    Darts44
    16th Apr 2020
    6:07pm
    We'll never know the true number. After every one be tested and re-tested, and re-tested...
    ozrog
    16th Apr 2020
    6:10pm
    Will be safer than any other country.
    older&wiser
    16th Apr 2020
    7:48pm
    Bad news - governments and authorities always under state. Good news - government and authorities always over state.
    Incognito
    16th Apr 2020
    8:49pm
    Which means more people should be sick and dying and they are not, so why do we need to keep restrictions in place? We don't.
    veepee
    17th Apr 2020
    11:29am
    Probably what they mistakenly thought in Japan and Singapore
    veepee
    17th Apr 2020
    11:25am
    No doubt there are discrepancies with numbers, which is the very reason that we have at least another 4 weeks of lock down. One would guess that the expert medical logic is that in that time many 'carriers' will have either shown symptoms, been isolated and contact traced or recovered and no longer pose a threat, and hopefully those infected by them will be minimised due to social distancing. In reality we probably need several more months of current restrictions to significantly risk. Our Medicos recognise this as they are saying that it will get worse before it gets better, they have seen what has happened in Japan and Singapore as restrictions were eased prematurely. Apart from some more privileged pockets of population, most Australians seem to be responding well to the restrictions. Sadly, the worst missteps have been by government agencies - the latest being the authority which decided that airline crews don't need to go into quarantine!!!! I don't think it takes a medical degree to see the lack of logic in that decision ;(


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