they are an issue affecting the whole world - but more specifically that it's happening now. Looking just a moment ago I see that nearly 5,000,000 (million) people have been killed by Covid. That includes about 750,000 just in the U.S.

If polio (or rubella, yellow feaver, measles, take your pick of any other disease that was once a huge problem and is now essentially a non-issue) were having a worldwide outbreak that had killed millions in the past 2 years I would hazard to guess that whether or not you were vaccinated would suddenly become an issue. But most of the U.S. is vaccinated against these diseases and we basically have herd immunity. So they're not a problem and we never think about them. These diseases once killed millions but since they don't anymore and haven't for a long time, it's a non-issue to us.