Inside the Brains of Bieber Fans. What's Behind Bieber Fever? Neuroscience Offers Explanation; a 'Safe' Infatuation. The symptoms include uncontrollable screaming, swooning and spending hours on Twitter and Facebook. It primarily affects preteen and teen girls, yet it is highly contagious and can infect mothers, too. In severe cases, sufferers camp out on sidewalks for days. "The appeal for me is, of course, that he's beautiful," says 15-year-old Emma Reeves of Madison, Conn., who has seen Justin Bieber twice in concert. "It's hard to find people who are successful, nice and care about other people and he has it all!" By disease standards, "Bieber Fever" is approaching a global pandemic with the release of the 18-year-old pop star's latest album, "Believe," last week.