The measles outbreak centered in northwest Texas grew to 683 cases and spread to three new counties on Friday, according to health officials. The latest update from the Texas Department of State Health Services adds 20 new cases since the agency's last update on Tuesday.

The Texas measles outbreak that began in Gaines County has grown to 683 cases, officials said on Friday. Ten of the impacted counties in Texas have “ongoing measles transmission,” although the state public health department estimates there are currently fewer than 10 confirmed cases still infectious.

With two confirmed measles cases in Travis County and a large outbreak in West Texas, do you need a measles booster? Here's what to know.