MRSA

It's very worrying but it's not HIV. Or anything close to as dangerous. And that might actually work in favor of restraining it. It hurts very badly, very quickly; it can be spread much more easily than HIV; it can be disfiguring; treatment can be as painful as it is drawn-out. So far, its main fatalities have been the elderly. So as an inducement for more care in sex, and more attention to hygiene, it's arguably more effective than HIV now is, because its physical impact is much speedier and more tangible. That's the optimistic side, at least.