But they have no symptoms!
http://www.freerepublic.com/focus/news/3352042/posts?page=31#31
Yup. So they are not contagious. But the risk of living with, sleeping with, or otherwise being in close contact with someone who has been exposed is that, if they do begin to exhibit symptoms, the risk is much higher that you will come into contact with the person’s now-contagious fluids.
Hence, the protocols recommend against close contact, but do not call for quarantine.