The measles outbreak in West Texas now counts almost 600 cases, according to Texas health data released Friday. The 597 cases is 36 more than were tallied Tuesday, according to information from Texas Health and Human Services.

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.

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