The Dallas County Health Department is investigating the death of a student who diagnosed with tuberculosis.
Hospital officials notified the health department that a North Dallas High School student who died of other medical issues also had tuberculosis.
She left school in October for health reasons.
Health officials are now trying to identify and test everyone whose came in contact with the girl.
The health department notified the school this week, and students said they were given letters to take home to parents.
But not all parents said they were notified.
Debra Lopez said she was unaware her daughter's school had any cases of tuberculosis.
Health officials have identified and notified all the students and faculty who have come in contact with the student and plan to conduct a series of skin test to see if anyone else was infected.
Dr. Michael Blackmon of Texas Health Plano said tuberculosis is not common in Dallas/Fort Worth area. The pulmonary specialist said the bacteria can be passed along by coughing and breathing in the infected air.
"It's very contagious," he said. "If you put people in a room in closed quarters, then you're going to spread this disease very effectively."
But doctors also say parents should not be alarmed.
"It's changed. We now have very good drugs. There no reason for anyone in Dallas county to die of the disease," said Dr. Garry Woo, Dallas County Health and Human Services.
Doctors say treating tuberculosis includes strong antibiotics and takes about two weeks.
Dallas County health officials said 195 cases of tuberculosis were reported in the county in 2009.