It's pretty much a case by case basis with events. RSA happened although some companies pulled out. I'm attending a smaller (but still fairly large) US event next week. It's still on but they're asking people to certify they aren't sick and haven't been to China in the last couple of weeks. (And some other precautions like a no handshaking protocol.)

This is the first one I've seen cancel that far out. (Well, I know another but I think there were other factors at play there as well.)