The photo in the linked article shows the American physician (Dr. Brantley), wearing full protective gear while treating Ebola patients last year. Either he got careless (highly unlikely); his protective gear failed, or the outbreak is much more widespread and Brantley was exposed in a location that was presumed safe.
Medical quarantines are one of the most effective—and cheapest—public health tools. But today are are rarely used, to avoid offending a particular group or interrupting international travel.
“... or Brantley was exposed in a location that was presumed safe.”
That would go along with the account of the doctor in post 1 that contracted it from a collegue that was not as careful as she was within the “hot” zone.