in quarantine. disease detectives are retracing her steps. who did she have close contact with? so far just one person who has been isolated. they will also try to answer the critical question -- how does a nurse following cdc guidelines wearing a face mask, two layers of gloves, shoe covers, leg covers, still get infected? we know some hospitals go even further with hooded tyvek suits, taping gloves to sleeves and suits to boots so not a fraction of skin is exposed. the same crews that decontaminated duncan's apartment are working on the nurse's. health officials are passing out information door to door. neighbors within a four-block radius of her building woke up to this reverse 911 call. >> please be advised that a health care worker who lives in your area has tested positive for the ebola virus. >> reporter: these neighbors