The Zika virus isn't exclusive to South America, as the pests that carry it have traveled farther north. I am unsure if these mosquitos would survive the trips home with athletes from all over the world, but it is certainly a cause for concern, and the effects of this should be closely considered to avoid such epidemic.
So many people are going to mingle at the Olympics that most diseases will spread more than they already have. Zika causes serious birth defects and we should do all we can to stop its progress, even if that means some athletes have to sacrifice their medals this year. Our health is more important.
The Zika virus is a serious threat, especially to women of childbearing age. However, I do not believe it will turn into a worldwide epidemic. We've heard about so many viruses and threats over the years, from the avian flu to ebola. These threats have been contained, and the Zika virus will be, too.
No, Zika is not a worldwide epidemic. It seems every time a new bug comes along there are cries of a new epidemic. Everything these days is an epidemic. It truly minimizes, and takes attention away from, real medical and scientific issues. Step back, take a deep breath and calm down.