Officials say the U.S. is seeing the worst measles outbreak they’ve seen in years.

The Centers for Disease Control and Prevention reports 159 Measles Cases since January 1 in the United States.

Those cases were reported in California, Colorado, Connecticut, Georgia, Illinois, Kentucky, New York, Oregon, Texas and Washington.

The CDC says measles is highly contagious but a two-dose vaccine is 97% effective against the virus.

The disease was eliminated in the United States in 2000 but is local in many other countires, which is how the current outbreaks started.