( CNN ) -- How did this happen ? That is what many people were asking Wednesday , after news broke that a health care worker had flown commercially at a time she was supposedly monitoring herself for a possible Ebola infection . Amber Vinson , 29 , is the third person to be diagnosed with Ebola in the United States -- after Thomas Eric Duncan , the Liberian national who fell ill after coming to Texas , and Nina Pham , who like Vinson had cared for Duncan at Dallas ' Texas Health Presbyterian Hospital . As with Pham , many questions surround how Vinson contracted Ebola despite efforts to prevent health care workers like them from getting the disease . Now they are compounded with others about safeguards for those who had contact with Duncan , who succumbed to the disease on October 8 , to prevent the disease from spreading further .
Sources : CDC official : Those being monitored for Ebola should be put on ` ` no - board '' list . Vinson flew commercially in the time she was supposed to be self - monitoring for Ebola . Dallas health care worker called CDC about temperature , was n't told not to fly , official says . The official says that Vinson should n't have flown commercially , used ` ` public transport ''