@Frogfish So what makes you think the scientists estimating 70-80% of the population of any given country will get coronavirus are wrong and your theory of the disease naturally “running its course” is right? What does “running its course” even mean - it disappears by some magic and stops spreading beyond a fraction of a % of population? Why would it stop?
The only rational explanation for why it hasn’t spread much in China and South Korea is because those governments’ aggressive contact tracing and quarantine measures worked. People who left Hubei province in December-January were traced and tested and their contacts and contacts’ contacts also tested and often quarantined. South Korea put together a massive intelligence operation to find every person who was in contact with the members of the church/cult that was the epicenter of the spread. Absent those proactive measures, there is nothing “naturally” stopping the virus from spreading and infecting majority of the population.
I've thought about that a lot and there are clearly other factors at work which contradict theoretical modelling (those 70-80% estimates were based on perfect propagation conditions with no preventative measures) none of which have come to pass in China, South Korea etc.
There are two obvious examples of this :
a) Historical data. Why would other diseases with an R value above 1.0 where social distancing and quarantining is not in effect not continue to spread throughout the population unabated? e.g. Common colds and flu (IQR: 1.19-1.37) ? Something is at work that mitigates the spread. Obviously vaccines have been developed over time however the % of people taking the vaccine is still extremely small compared to total populations.
b) Everyone agrees that in its early stages (before it known to be spreading in the population) the rate of infection is exponential over a period of 3-5 days. By the time quarantines and social distancing are introduced it has already spread widely however the exponential growth reaches an inflection point and infections start to drop off (China & South Korea) dramatically.
How is it possible in a country with a population of 1.6 billion that the late introduction of preventative measures stopped it dead? Look at the figures for Shanghai and Beijing (both just a few hundred infected) and pretty much every other major Chinese city. Preventative measures (and nothing like Wuhan) were not introduced until much later yet there was no transmission explosion.
As to the considerations of quarantines and social distancing working and your statement that contact tracing was responsible for the virus' spread being halted. To claim the thousands that traveled out of Hubei (internationally and domestically) were traced is completely illogical (and clearly untrue). Wuhan airport handles over 25m people annually, late Dec/early Jan this year was PRIME time for movement due to the Chinese New Year so between 75,000 and 150,000 people per day moving through the airport. Fancy tracing that lot ?
Look at the timeline to understand that it was a case of shutting the stable door after the horse had bolted. And that's not even considering the now widely accepted figure of at least 10 times more people are infected than official figures (and that the testing is far from 100% successful at identifying the infected - 2 or 3 tests often being required at different stages for confirmation).
It may surely slow down the spread, if caught in the early stages, but there are limiting factors and all Govts gave up on contact tracing all the infected very soon after the initial outbreak (look at China. South Korea and Italy, there are simply not enough personnel and people's memories are just not that good (to say nothing about all the unknown people they were in contact with - consider a ski-slope or a football match for example).
What this proved was that contract tracing was ineffective if the virus spread was not caught within the first week or two and within a limited area .... and of course it wasn't. Contact tracing in China didn't even begin until they realised there was a serious issue (around 3 weeks after Ground Zero).
The fact is that the numbers simply don't support the theory that quarantining and social distancing alone can quell an outbreak. Or your quote that 70-80% of the population may become infected (actually the real number is far far from it, it's a miniscule %, way way under 1%, in both South Korea and for China : 0.0005% of the population).
I gave you the Timeline for China above and for South Korea it will be something similar. Simply because no country shuts down when they only have a few infected (and when the disease's potential has not been identified), they gradually introduce measures but as the timeline shows the virus has long been spread before that happens.
