A health care worker in Dallas, Texas has tested positive for Ebola in preliminary testing.   Confirmation testing will be done at the Centres for Disease Control and Prevention in Atlanta.  If confirmed, it would be the first known case of Ebola being contracted or transmitted in North America. 

The health care worker was one of the people involved with looking after Thomas Eric Duncan, the man who died Wednesday in isolation at Texas Health Presbyterian Hospital. 

Duncan was the first person diagnosed with the deadly virus in the U.S. after contracting it in Liberia.