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Why the Coronavirus could be spreading exponentially

The Australian Government continues the argument that ‘Case numbers of Covid-19 in Australia are dropping’ and that we are ‘flattening the curve’ of transmission. Until we can test everyone with symptoms this is a potentially dangerous message that needs to be stopped. Exponential curves always appear linear in the beginning, or in plain English, at the beginning of any pandemic, the spread initially can look slow but the numbers can be secretly growing and we don’t realise it until our health systems are about to be overrun (America, especially New York, is the best current example). I have outlined below why Covid-19 is such a tricky disease to monitor the spread of in the first few months of the pandemic arriving on Australian soil:

- There is a large lag time between infection and symptoms and very large lag time between symptoms and death. It takes on average 7 days to become symptomatic after a person has been exposed to Covid-19, but they can spread the virus for 48 hours before they become symptomatic. It may take another 7 days after symptoms to get sick enough to require hospitalisation and it can take 3-6 weeks after symptoms have developed to die.

- In Australia we currently have a testing criteria confirmation bias. Until only a few days ago, the testing criteria was that to be tested, you had to have recently returned for overseas, been in contact with a known Covid-19 sufferer or be sick enough to present to hospital. This means a raft of people with mild symptoms do not meet the testing criteria.

- The test for Covid-19 is an antigen test. It lets you know if you have an active infection. This test will be negative after you have fully recovered from the virus. Australia needs to make a huge amount of these tests available, along with the antibody test that can tell you if you have had the virus and are now likely immune. Only the antibody test will tell us how many people actually had the disease and went completely undiagnosed.

- Asymptomatic carriers: Carriers can have a wide range of experiences, from being asymptomatic, to mildly unwell, to acutely unwell to needing intensive care treatment. Asymptomatic carriers can be moving around in the community, spreading the disease completely unaware.

- The disease is spread in respiratory secretions as aerosol contact and spread in faecal material. This means that a carrier can spread the virus in their breath and spit (including cough and sneeze). If they touch their mouth, their hands are contaminated. They can also spread the virus in their stool which has huge implications for childcare centres, where children are toilet training or having nappies changed. Even primary school aged children are generally not capable of having the hand hygiene required of them to not spread the virus to their classmates and friends (and families)

- Infected people may infect on average 2-3 people, but some people are super spreaders and others may spread it to nobody. We know that children tend to be asymptomatic or have mild symptoms only. For example, an asymptomatic toddler at day-care could potentially infect the whole room they are in during the (approx.) 7-14 days they are shedding the virus, in turn, every infected child from that day-care facility would infect their whole household.


Let’s imagine 3 people out of a few thousand who attended the Hillsong Convention on the 14th March were positive for Covid-19. See the diagram I have included in the blog. They thought they just had a sniffle. They were all young and infected 3 young people each when they hugged each other hello. That is a total of 12 people infected. The initial 3 people recovered completely (and their antigen test will be negative by March 28, so they will never know they were infected)

To keep this simple, I’m going to imagine everybody has an incubation time of 7 days

The 9 carriers only get symptoms on the 21st of March, as they are young, many of them only have mild symptoms, some feel a bit worse but (to keep it simple) they all spread it to 3 people. There are now 39 people infected. These 9 people will have negative antigen tests by April 4

By the 4th of April, 120 people are infected (including 3 recovered) but 81 of those haven’t shown symptoms yet

By the 11th of April 363 people are infected, 18 of them have symptoms severe enough to present to hospital.

By the 18th of April, 1092 people are infected, 54 people have now presented to hospital, one has died.

If Australia then decided to go into lockdown, by the 24th April, 163 people are in hospital 11 of these will die. Not many of them met the testing criteria as it currently stands as they did not travel overseas or have contact with a known Covid19 sufferer as the initial 3 did not know they had Covid-19 and by the time they even think they may have had it, they test negative to the antigen test. This is only from 3 initial people at a convention, but who knows how many people were already spreading Covid-19 in our community. Likely a lot more than just three people. We just don’t know.

The lesson from this:

This is one very small example of what is likely happening in Australia right now. The Ruby Princess, for example, let people off the boat on March 19, how many people did those carriers infect as they were walking around Sydney? At least they are being tracked now but how many people did they pass by in the general public who will never know they had contact with them?

The only solution is to go into lockdown now, stock up on millions of antigen and antibody tests, acquire PPE, enforce mandatory cloth mask wearing in public and for goodness sake, find some toilet paper. Then, in 3-6 weeks’ time, we will know what we are dealing with.

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