There is so much travel between South America, Brazil and the rest of the world, anyway that to think you're gonna have a substantial impact by cancelling the Olympics. I don't think is scientifically based. That's not say you shouldn't take Zika very seriously and let me reiterate, so that there's absolutely no confusion.
If you are pregnant, you don't go. If you're a man and you go there, you practice certain types of safe sex activity, depending upon your situation and who your sexual partner is. If she's an individual who is already pregnant, you have to be very careful. Use a condom for the duration of the pregnancy.
All of those things are very important. That's different than saying, you're going to cancel the Olympics and that's the reason why the WHO does not agree with the signatures of that letter. Tom Frieden at the CDC doesn't agree with them and I don't agree with them.