Texas health officials have issued a measles alert and are urging people to get immunized after more than a dozen cases were reported this year.
Authorities said no cases were reported in 2012.
The Texas Department of State Health Services said Texas has had 11 confirmed cases so far this year, based on the latest figures released on Friday.
Six cases confirmed in the last week were in Tarrant County, the department said, but county public health officials in Fort Worth later updated that number to report a total of nine cases.
Dallas and Denton counties each reported two measles cases, Harris County has one.
Agency officials said Texas had six reported cases of measles in 2011.
State health officials are asking health care providers to watch for potential exposures and patients with measles symptoms, especially in North Texas, the agency said in a statement. Measles can be spread by contact with an infected person through coughing and sneezing.
Tarrant County Public Health experts traced some of the area's measles cases to an adult who had traveled outside the U.S., the agency said. Further details about the person and where he or she traveled were not immediately released.
"Measles is so contagious that if one person has it, 90 percent of the people close to that person who are not immune or vaccinated will also become infected with the measles virus," according to state health officials.
People should check their immunization status with their health care provider, the agency said.