North Texas doctors are seeing an uptick in cases of pertussis, which is more commonly known as whooping cough.
So far this year in Tarrant County, 135 cases have been reported.
A student at Nolan Catholic High School in Fort Worth is the latest case. The school sent a letter home to parents telling them of the case and to monitor their children.
Administrators told NBC 5 that the sick student is not in school at this time.
Dr. Jeffrey Kahn, the director of infectious diseases at Children’s Medical Center in Dallas, said the hospital saw 14 cases in all of 2011 but had 113 cases this year through November.
Kahn said younger children -- infants to six months old -- are hit the hardest. Even though the children could have already started their pertussis shots, their immune systems aren’t strong enough to fight the highly contagious cough, he said.
Children usually contract the cough from family members, Kahn said.
"Basically, all the cases that we've seen here -- very young children -- there's a history of someone in the household who has had a long chronic cough and they don't recognize that cough as being pertussis," he said.
The cough is treated with an antibiotics regiment, Kahn said.