There have been four measles cases reported in the Dallas-Fort Worth area this year: one in Collin County, one in Denton County and two in Rockwall County. State authorities have not officially tied any of those cases to the outbreak that began in Gaines County, and all four appear in the state public health department’s list of “other 2025″ cases.

The outbreak would have to spread continuously for more than a year to undo the U.S.’s achievement.

As more counties are being impacted by the ongoing measles outbreak and added to the growing list of counties across Texas, here's what to know.