NOTE: The first version of this article was based on the Daily Mail article:
CORRECTION
Looking at the video by the researchers, for which I’m grateful to Kate Brewer) to the link:
https://covid.joinzoe.com/post/covid-research-update-uk
it says that 25-30% of respondents reported ‘some COVID-like symptoms associated with COVID’. It also usefully clarifies that most of the early respondents were likely younger people. This is very different from the 1.9M reported in the DM article and which I re-used in my blog. Humble apologies, I didn’t check the source. Now that I have, I am still unable to find the other figures the DM quoted, so perhaps they used a different source.
So, using the revised figures ….
The coronavirus symptom tracking app results suggest, according to Tim Spector, that 25-30% of respondents reported ‘some symptoms associated with COVID’. Without proper testing, it’s as good an estimate as we’re likely to get. Extending to the whole UK population, there could be 16-20M people who have already had the disease. (As an aside, and I don’t trust Chinese figures, some reports suggest that 20% of people who are infected develop symptoms. For 25-30% to report symptoms, that would mean almost everyone in the UK would need to have been infected).
The app is a sort of self-selected, self-reported test, but presumably proper tests on a proper sample of the population would reveal more. If you’re trying to solve a problem, knowing its dimensions can make a huge difference to the solution you will pick.
If their figure is true, then only 0.2% – 0.25% of people who have had the disease developed into official cases. But we have no idea how many have been exposed to the virus and not even had enough symptoms to become part of their 25+%. It could be anywhere between 25% and 50% (as other studies have cited).
If true, we might already be a quarter or even half of the way through. We might only see another 40,000 – 80,000 cases, even if lockdown is lifted
So far, 3605 deaths have been announced in the UK from 38,168 cases, but the ONS says the death toll could be 20% higher, at 4325. That gives an 11.3% death rate in the UK but that doesn’t include documented cases that will die later (the numbers that have been listed as ‘recovered’ are only a tenth of the deaths, so that is an important caveat). So the UK figure is likely to be much higher than the 11.3%. On the other hand, as Peter Hitchens has often pointed out, that figure is for all deaths that occurred of people who had the disease, not those who died mainly because of it, very different. Large numbers of elderly people die every year. Every day, around 1650 people die in the UK. Any of those who died from the usual causes but also had COVID would appear in the COVID deaths figures, along with any who did die because of it but would have died in a few months of something else anyway.
Without proper testing of a large and representative sample of the population, we really have no idea how many people have actually already had the disease or are resistant, and without proper recording of deaths, how many known cases are still going to die. Only when we have proper large scale test results will we be able to estimate how many future infections, cases and deaths there might be as the result of lifting lockdown before the disease has been eliminated.
However, a simple calculation using the above suggests that if lockdown were lifted, there might only be 10,000 – 13,000 more deaths that might list COVID on the death certificate, and the number of deaths primarily due to COVID would be far less. Perhaps only a very few thousand more people will die because of COVID if lockdown is lifted.
If it really is only 3000 – 5000, there are far better ways to save that number, such as cleaning hospitals better.
Timeguide - The future before it comes over the horizon 
You might have more up to date info than me, but looking at the corvid tracker app I actually get even better figures; of their sample of 2 million, 400000 had symptoms and 13% of them probably have corvid.
Extrapolated directly the the uk pop that gives you 2 million. Let’s assume there is a bias in the sample and only assume 1.5 million. Now lets assume (as per iceland) a 50% asymptomatic, so about 2 and a quarter million are currently infected.
But we’ve got to get there somehow; Using a R0 midway beween WHO (2.2) and fergunson(3), we can work out on average how many people in each ‘generation’ of the virus and add them in as corvid immune, which gives us just under 4 million, nearly 5 % of the population.
Of course IANAS (I am not a statistician) just someone interested in the numbers.
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I have since been pointed at the video by the researchers that stated 25-30% of respondents had some of the symptoms, not far off what you quote. I edited my article to reflect that since it was very different from what the DM article said. I don’t have up to date data, and am looking for some.
The future prospects do look very much better with the revised figures, and suggest that maybe only a few thousand more will die even after we lift lockdown. That would be good.
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