A total of 159 people have contracted measles in Texas as of Tuesday, according to the state’s health department, marking another increase in an outbreak of the highly contagious virus that was first reported in the state in late January.

In 2000, the CDC declared that measles had been eliminated from the United States. But now America is at risk of losing that status: A measles outbreak has sickened more than 150 people in Texas and New Mexico since late January.