School and health officials announced Thursday the investigation of a possible case of pertussis, commonly known as whooping cough, at Western Middle School.

The case could also affect Western Alamance High School, as the student under examination rides a school bus shared between the middle school and high school. the number of the bus the student rides, as well as the number of students who share that bus, wasn’t available Thursday.

The student’s case hadn’t yet been confirmed by lab testing. Results of those tests are expected by early next week.

Health department officials had identified 84 families with children at risk of contracting pertussis and as of Thursday night had made contact with about 75 percent of those families, said health department spokesman Eric Nickens Jr. the remaining families would be contacted Friday, he said.

Students found to be at risk for pertussis will be encouraged to begin taking a course of azithromycin, an antibiotic. the cost of the drug runs between $14 and $45 at most pharmacies, said Communicable Disease Program Coordinator Ayo White.

This case isn’t believed to be connected to eight cases confirmed at and around B. Everette Jordan Elementary last month.

Alamance-Burlington Schools notified the Alamance County Health Department of the possible case Thursday morning. the student was in “close contact” with someone who had a lab-confirmed case of pertussis, said Dr. Kathleen Shapley-Quinn, the health department’s medical director.

The student’s age, grade and sex weren’t being released Thursday, health department officials said, though Shapley-Quinn referred to the student as “she” and “her” several times during a news conference Thursday afternoon.

The student, who has been vaccinated against pertussis, has been sick for about a week. Pertussis symptoms — including a runny nose and low fever that progress to fits of five to 15 coughs with no breaths between — can take as long as 21 days to appear.

An investigation into the possible spreading of pertussis will initially involve students who were within 3 feet of the individual for 15 minutes or more, White said. the investigation could expand if other cases are identified.

Pertussis is considered a major health threat to infants, who don’t have the lung capacity to handle the coughing fits. For older children and adults, the illness causes more discomfort than health risks, Shapley-Quinn said.

Students at Western Middle and Western Alamance have been vaccinated against pertussis but the vaccine’s efficacy can weaken as children and adults age and infection by the bacteria that causes the illness is still possible in some cases, Shapley-Quinn said. Children and adults are encouraged to receive a Tdap booster vaccination to help prevent the illness’ contraction and spreading.

The health department isn’t recommending that parents keep healthy children home from school. If parents are concerned that their children might be ill, they should contact their primary physician, Shapley-Quinn said.

Parents and families of students believed to be at risk for contracting pertussis will be contacted by the health department, said department spokesman Eric Nickens Jr.

Other parents and residents concerned about pertussis can call 336-516-7715 and speak to a nurse. Nickens encouraged residents to leave a message at that number if they didn’t get an answer and said that all messages would be returned by the department.