Measles cases have increased to their highest levels since 1996 in the United States, with almost half of those cases involving children who were not vaccinated, health officials say.

This is a troublesome development because health officials declared measles eliminated in 2000.

Centers for Disease Control and Prevention did a study and found that there were 131 measles cases for the first seven months of 2008 so far this year, versus 42 cases for all of 2007.

In addition, the CDC found that many of those cases were home-schooled children who are not required to be vaccinated.