Parents in the Burlington Township School District are being warned that a middle school student was recently diagnosed with whooping cough.

The school district sent a letter to parents this week notifying them of the illness, which is known as pertussis and for which there is a childhood vaccine.

"This is a contagious respiratory illness that spreads from person to person when the infected individual coughs or sneezes," the letter says.

The disease is "very contagious" and is typically mild in older children and adults, but very serious for infants, according to the Burlington County Health Department.

The health department says all New Jersey sixth-graders must receive the tetanus and diptheria toxoids and acellular pertussis vaccine, known as Tdap. The school district said it couldn't disclose the infected student's immunization status.

Symptoms usually appear five to 10 days after someone is exposed.

Pertussis generally starts with cold-like symptoms and a cough that worsen over one to two weeks.

The symptoms generally include long coughing fits followed by a whooping noise. Severe coughing fits may be followed by vomiting, turning blue or difficulty catching one's breath, officials said.

The cough is often worse at night and does not respond to cough medicine.

The school district says students should not go to school if they show any signs of pertussis.

If a child is coughing for several days, he or she should see a physician, who should be told that a student at the school was diagnosed with whooping cough, the district advised.

Parents with questions can contact their child's doctor, the school nurse or the county health department. The school district can be contacted over winter break by e-mailing mbell@burltwpsch.org.