ROANOKE CO., Va. -

The Health Department is warning parents at a Roanoke County school about a case of pertussis.

In a letter sent to parents of Northside High School students, the department says an attendee of the school recently got whooping cough. School officials haven't said exactly when.

They think the exposure has been limited and no further testing is needed.

Students who get a nagging cough should get checked by a doctor. The department recommends getting the pertussis vaccine.

According to the Virginia Department of Health, pertussis can be serious for infants and young children, but affects people of all ages.

It's spread through the air by coughing and is highly contagious.