The first case caught in the USA - from Reuters:
Texas health worker becomes first person to contract Ebola in U.S.
A Texas health worker has contracted Ebola after treating a Liberian who died of the disease at a Dallas hospital last week, raising concern about how U.S. medical guidelines aimed at stopping the spread of the disease were breached.
The infected worker, identified as a woman but not named by authorities as they announced the case on Sunday, is believed to be the first person to contract the disease in the United States.
All it takes is for this to gain a foothold. The R0 value for Ebola is two which means that for every infected person, two subsequent people will become infected. It grows, it doesn't die out unless the infected population is very small and remote.
