Blood samples are seen in a hospital testing for tuberculosis. (credit: RODGER BOSCH/AFP/Getty Images)

ENNIS (CBSDFW.COM) - Follow-up testing for tuberculosis begins Monday in the Ennis school district.

Since the beginning of the school year, Ennis High School students and staff have been through rounds of testing and a host of protocols after learning a teacher, who held class last year and over the summer, had been diagnosed with tuberculosis.

While the infected teacher didn’t report to class in the fall, school district administrators ordered testing for the entire high school.

Around one dozen people tested positive for TB. More than 200 tested positive for a latent, non-contagious form of TB and everyone else tested negative.

“All of the students who were affected by the situation are back in class at this time and we’re very encouraged by that,” said Ennis School Board President Dr. Mack Boyd.

The re-testing, set to begin Monday, is for those who tested negative. State health workers say the a second round of tests are routine and is done to make sure no one has come down with the illness since the initial outbreak.