Centennial Elementary School in Plano sent home notices warning about cases of whooping cough that had been diagnosed.

PLANO — Whooping cough is a highly contagious bacterial disease that was nearly eradicated. But the disease — also known as pertussis — it's making a comeback.

And that's causing experts to re-examine recommendations for preventing it.

Two students from Centennial Elementary School in Plano stayed home with the disease this week, and others have symptoms.

Holden Halbach, 8, did not look sick, but he was quarantined for five days with whooping cough.

"We were just flabbergasted," said Betsy Halbach, Holden's mom.

At first, the third grader did not show any symptoms, but another boy in his math class was diagnosed with whooping cough.

"A friend said, 'maybe you should get it checked,'" Betsy Halbach said.

Holden, and at least five of his friends, came down with slight coughs. The others were waiting for their test results, Monday.

"At this point, there haven't been any cases of whooping cough outside the third grade," said Janet Glowicz, Collin County Health Services.

Centennial Elementary has sent home two warning notices saying a student or teacher had been diagnosed with whooping cough.

Nationwide, more school-aged children are coming down with whooping cough. That's why, for the first time, the federal Health and Human Services s now offering a booster to anyone 11-years-old or older.

Whooping cough first presents itself with nasal congestion and possibly fever. A mild cough can get worse and can last two to three months. Once patients start taking antibiotics, they are no longer contagious after five days. Infants are most at risk. Last year in Texas, eight children died from whooping caugh.

"If your child is attending the school and doesn't have any symptoms, they shouldn't be concerned," Glowicz said. "They should pay attention if [a child] develops sinusitis. They should let their doctor know that their child may have been exposed to whooping cough."

E-mail mjepson@wfaa.com.