[lopmotr]

You're applying conventional knowledge to an unusual situation where it doesn't apply. The current test in my country is something like "was sitting within 4 rows of a known patient on a plane". That's obviously got a massive false positive rate but we do it anyway. The action you take when officially tested positive is the same as you take when learning you had contact with a patient - isolate yourself at home. There's no wasted drugs because there's no treatment for it! At worst, you might do an official test, but if those are in short supply, they're not going to be given to anyone who just walks in with a home-made result.