Prediction: no test development will be faster than the spread of the disease so when tests are easily available many or most densely populated areas will be at over 50% immunity.
As you say "the" disease I assume you mean Covid19, not just a future disease. AFAIAA is not been shown that recovered (or long-term asymptomatic) cases are immune and there's some suggestion that at least a few people don't have immunity after recovery. I think I'd stick with "at 50% infection rate".
But then if at 50% infection rate you've had 0.2% death rate (seems to be about the right order for confirmed deaths+anticipated numbers of not confirmed {ie excess deaths during the period of the diseases spread}, in UK) then testing might save huge numbers of deaths.
The death rate in the second half of the population I'd expect to be higher, they include those with pre-existing conditions (including the more elderly) who isolated early, testing of the caregivers and families will be very important.
Yes - I’m only talking a about Covid. This can definitely be interesting for Covid-31 though.
Testing and contact tracing will indeed save lots of lives, I’m just not optimistic about <$1 “daily tests for everyone” within the relevant time frame of this pandemic.
