Updated at 6:23 p.m. ET
Hundreds of students and faculty at two universities in Los Angeles have been asked to stay home unless they can prove that they've been vaccinated against measles.
The LA campuses of the University of California and California State University imposed the quarantine after they became aware of people infected with measles who had potentially exposed hundreds. At UCLA, a student exposed at least 500 people earlier this month; at Cal State, someone with measles went to a library and encountered hundreds.