(CNN)To contain a measles outbreak, a newly infected person has to work in tandem with state and local health authorities, providing information on when their symptoms began and whom they may have exposed during the nine days they are contagious.

Most people do. Then there are those who refuse.
Just last week in Rockland County, New York, which has been battling a persistent outbreak of measles in the Orthodox Jewish community for six months, a contagious person stopped cooperating with local investigators.