Measles cases exploded in the southwest this week, with more than 483 cases confirmed in 21 states, the CDC said Friday. That’s a 360% surge from the week prior, when just 105 patients were reported with measles — sparking widespread concerns that the outbreak of the once-rare virus will continue to spread across the US.

The United States is facing its largest measles outbreak in years. As of March 28, the Centers for Disease Control and Prevention (CDC) confirmed 483 measles cases across 20 U.S. jurisdictions, with Texas reporting the most severe surge.

HOUSTON — A measles outbreak in the South Plains and Panhandle regions of Texas continues to escalate, with the Texas Department of State Health Services now reporting 327 confirmed cases on Tuesday morning, March 25, since late January.