Dunno if this was posted already (article in Norwegian), but Iceland is now testing a sampling of asymptomatic, arbitrary people in Reykjavik. Approximately 1% of the tests have come back positive. 52 of 6163.
Island tester tusenvis av helt friske personer – nå skal Norge følge etter
Iceland's confirmed cases is 0.25% of the population, and Iceland currently leads the testing with 25,000 tests per million. 0.25% is a lower bound, but it's closer to the real number of symptomatic people than all other countries due to intensive testing.
This is good: These numbers can be used to give an idea of how quickly the epidemic will burn through the whole population. The 1% number should be reasonably accurate for total asymptomatic cases in the communities that have been sampled. The real number is probably a little higher, due to people who got the virus and got well, but it won't be much larger since most infections happened very recently or are still ongoing.
1% is a lot more promising than a worst-case scenario of say 0.1%, which would imply that lockdowns or extreme measures have to be in effect for
years if we're to get through this without overloading the healthcare system all the way through. Iceland's data supports what other early data indicates; 50-75% cases are asymptomatic.
This is admittedly much worse than the dream/fantasy scenario of the British preprint study that (with some major & shaky assumptions) estimated 60% of the population has already had the virus. We can probably discount that hope, but the real situation seems to be much better than the worst case.
Herd immunity for Covid19's level of transmissibility is estimated at a 60% cumulative infection rate, but some brief reasoning implies that milder quarantine measures (contact tracing, mask usage in public, intensive testing of symptomatic cases, probably certain quarantine measures regarding crowds) will have good effect even before this number is reached. Ditto for warmer climate during the summer months, which won't stop the epidemic in its tracks, but will similarly have a positive effect on the R0 number (new infections per case)
Iceland is already on the order of 2,5% of the way there, with a cumulative infection rate of ~1.5%.
Let's say Iceland has twice the number of symptomatic cases reported (0.5%) and the number of asymptomatic cases is representative (1%). This means that you can multiply the number of symptomatic cases by 3 to estimate the total/cumulative number of infections. And most countries don't catch
nearly as big a portion of the symptomatic cases as Iceland does. Look at the number of dead compared to the confirmed cases to get an idea.
I haven't done the maths for the US yet, but it should be more promising even though the body count will look extremely bleak in the following weeks.
Tl;dr: if herd immunity is possible, it can be achieved in a reasonable timeframe. We're already making good progress. Probably not most of the way there yet, but it won't take years.
