An outbreak of measles in the South Plains of Texas is continuing to grow, with the number of cases doubling in less than a week. At least 48 cases were identified with symptom onset within the last three weeks,

In the last three weeks, 48 cases of measles have been identified, sending 13 patients to the hospital, according to the Texas Department of State Health Services.

Nine of those infected were hospitalized and more cases are likely, health authorities said. U.S. vaccination rates for measles are falling, according to the CDC.