If 80% of the population get coronavirus, who are the other 20%?

[KenDodd]

Why don't they get it?

Where are you getting this 80% prediction from?!

Introverts. We are antisocial but safe

What do you mean “who are they?” they’re just going to be people who didn’t get it.

What an odd question. Those people who are lucky enough not to get it.

But the 80% is a worst case (but not impossible) situation. Other studies have said 60%

Those who have taken sensible precautions and not mixed with others will obviously have a greater chance of avoiding the illness.

Lib Dem voters.

Presume this is about the chief medical officer’s statement that “we know that it will not go above 80%”
How go they know that for sure”

pristine 👍

I meant - How do they know that for sure?

Previous flu epidemics?

Do you mean are they immune? I heard that some people are immune to HIV and they can be traced back to people who survived the plagues! I wonder if it's something similar?

I think this is based on the theory that people who have already had it act as though they have been vaccinated. Let’s say for simplicity every person with this virus currently infected two people. This means currently it is doubling

Probably because they have a lot of experience in looking at home diseases work and what proportion of populations are naturally resistant. (and it is likely to be natural resistance that is key, not relying on 20% of the population to not mix with other people for the next 3 months).

@nellodee I think there is some evidence that you can catch it twice...

Oops pasted too soon. But if out of the two people it would have infected, one of them was already immune, it’s not doubling any more. Those immune people dampen an eventually kill the spread.

The evidence you can catch it twice is very weak. There’s been a very small amount of cases where someone has tested positive, then negative, then positive again. Although this could mean people could be infected, it’s far more likely to have been a false negative in the middle test as there have been many, many instances of false negatives with the tests we have at present. Apparently lots of the people taking the swabs are not fully trained, in addition to there being flaws with the tests themselves.

Some will have natural resistance, some will catch a very mild case and not realise and some will be 'lucky' (just happening to avoid the virus/ being an isolated type of person/ hygiene measures paying off at just the right moment) - statistics on past viruses & outbreaks suggest to them this group has to form at least 20% of population, that's all. If you think about it, the spread getting to 100% is massively unlikely, unless people deliberately tried to infect themselves there'd always be people who somehow avoid the virus.

Presume this is about the chief medical officer’s statement that “we know that it will not go above 80%
How go they know that for sure

@ceeveebee In short, epidemiologists track how many people each infectious person has passed the disease to (when they not in isolation) and calculate the average. It's called the reproductive number for the virus. You can use that to model what percentage of the population needs to be immune (from catching the infection or vaccination) before the virus can no longer be transmitted between people because there aren't enough susceptible people to infect so you have herd immunity.

Here's an explanation: en.wikipedia.org/wiki/Herd_immunity

Ok, they are just the last to come into contact with it by which time enough people have had it to create herd immunity?
Or they're naturally immune?

I didn't think it was possible 20% of the population could live by themselves on top of a mountain!

Woodworkers.

I assume it is a mathematical model they have done that shows that when 80% of the population is immune ( through having caught it or from the rareity of natural immunity) then the virus is not able .to find enough people to move between as the number of people who are not immune are spread too thinly so it dies out.

This model would have lots of assumptions built in based on observations about how contagious the virus is etc so is probably a worst case scenario, given the data they have.

@nellodee I don’t think your maths is right there. If everyone who catches it then goes on to infect 2 people, that’s not doubling - that’s exponential growth.

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 etc. Numbers increasing very quickly.
If it spreads exponentially (and I’m not saying it does).

I saw a map about how it might spread through the UK and noticed an assumption it wouldn’t spread to the far north west of Scotland. What a load of shite. Loads of tourists head that way. It’s as likely to get to north west scotland as it is anywhere else

Anyway I suspect the 80 per cent is based on projections relating to the naturally immune or those who don’t realise they have it or pockets where it doesn’t spread

People who wash their hands, don’t sticky grubby fingers in mouth and haven’t got sneezed on by someone infected.