Re: How will they know it's a false alarm?
It is far safer to have the false positives.
That depends entirely non how many real positives there are.
Assume that you have a test with a 1% false positive rate (which is extremely good, 2-3% is more likely).
Test 1m people, of whom 200K actually have it. 1% of the 800K who don't will show up as (false) positives, that's 8K. Not so bad compared to 200K, perhaps.
Now consider the end of the epidemic, when only 1000 people still have the virus. 1% false positive rate of the 999,000 uninfected people is 9990, that's 10x the actual infection rate and makes the test largely worthless.
Biting the hand that feeds IT
