California health officials say the number of people in the state infected with measles is now up to 59.

Health officials said Wednesday that of the 59 cases, 42 have been linked to visits to Southern California Disney theme parks last month. Among those infected are five Disney employees.

Most have not been vaccinated against measles.

Measles is a highly contagious illness that can be easily spread through the air. Though the virus has been eradicated in the U.S. since 2000, it can still enter through an infected traveler.

A handful of other cases have been reported in four other states and Mexico.