Close, sustained contact. That, health officials have repeatedly said, is the only way that the Andes hantavirus, which caused an outbreak on a cruise ship and has gripped the world’s attention, spreads among people. “You have to be in close contact with someone who has a lot of symptoms,” Dr. Jay Bhattacharya, acting director of the Centers for Disease Control and Prevention, said in an interview on Fox News. But scientists who have studied hantaviruses for decades are far less certain about