WINDHAM, N.H. (WHDH) -- Two students at two New Hampshire elementary schools were diagnosed with whooping cough.

The Windham Center School and the Gold Brook School have been affected. School and health officials said the number of whooping cough cases could rise.

“I just heard about it today,” said Colin Campbell, a fifth grader.

Parents got a letter warning them of the danger: The pertussis leads to terrible coughing fits resulting in a whooping wound, which are sometimes accompanied by gagging, vomiting or difficulty breathing.

“It is extremely contagious. It requires you to have some type of immediate contact for it to be transmitted so, therefore, the youngsters who were in the classrooms with the children were at the greatest risk,” said Dr. Henry Labranche, Superintendent of Windham schools.

Parents are wondering what to tell their children.

“I haven’t even talked to them about it because I’m afraid they’ll be more nervous or frightened,” said Ann O’Connor, a parent.

Labranche called in cleaning crews to sanitize classroom areas where the infected children studied. The affected students have to stay home at least five days while taking antibiotics.

There are also whooping cough vaccines available.

Whooping cough has about a week-long incubation period.