the problem is this guy boarded a plane from Liberia and got past security screening.
time line from last night's news reporting:
Sept 19 left Liberia
Sept 20 arrived in Dallas
Sept 26 guy goes to ER, he did not provide any information where he had been - they sent him home with antibiotics
Sept 28 same guy gets transported to ER by ambulance and is diagnosed with Ebola - this is when they discover he had been in West Africa
the same ambulance was used for those 2 days as well as exposing the EMT's - the EMT's are now in a 21 day home quarantine.
The news report first indicated just a handful of people this guy came in contact with but at last count they had identified at least 18 people, they are trying to locate those people and indicated a 7 day period to find them in case any of them are infected.