"The freelancer came down with symptoms on Wednesday, feeling tired and achy. As part of a routine temperature check, he discovered he was running a slight fever," said NBC's website.
"He immediately quarantined himself and sought medical advice."
The man, who was only hired on Tuesday, went to a Medecins Sans Frontieres (MSF) treatment centre to be tested on Thursday and the positive result came back just under 12 hours later.
He was a second cameraman for NBC News chief medical editor and correspondent Dr Nancy Snyderman, who is reporting on assignment in Monrovia with three other NBC employees.
He is the fourth American to have contracted Ebola in Liberia. The other three were Christian missionaries who became infected in healthcare settings.
The cameraman's name was not revealed but NBC said he "has been working in Liberia on various projects for the past three years".
The first case of Ebola diagnosed in the U.S. has been confirmed in a man who recently traveled from Liberia to Dallas, sending chills through the area's West African community whose leaders urged caution to prevent spreading the virus.
7 years, 3 months ago