Related: How will survivors of a global plague find each other? The global plague struck fast and killed almost all of humanity. Only those that were immune to the plague survived (so basically the plague is extinct). read more
This is a much more serious situation than a plague affecting 99% of men. It will be catastrophic for humanity if the plague continues, but survivable if it's a one-time event. read more
If 99% of women were left infertile, this would be an extremely serious issue; women can have only so many babies. But 99% of men is not so bad. Assuming the plague is a one-time event, there would still be 1% of those males able to impregnate 100 women, either the direct fun way or through sperm banks. read more
In a megacity of 10 million people, there'd be only 1000 people spread out over tens to hundreds of kilometers. It'll take a while to find other people, but I'm sure in the event of 99.99% of people suddenly disappearing, these people would group together over the course of a few weeks. read more