So, I gotta question

How many people has this health care worker been in contact with for the last, say, week?

The answer is this; no one knows.

Just let this bit sink in,

"The new case in Texas indicated a professional lapse that may have caused other health workers at the hospital to be infected as well, said the director of the Centers for Disease Control and Prevention (CDC)."

Makes you squirm, dunnit?

Juuuuust about to seal the door, because it's the only way to be sure.