The Garrett County Health Department has confirmed a case of pertussis, commonly known as whooping cough in an 18-year-old resident of the county. The case is being investigated and health officials are working to identify and notify close contacts to prevent further spread of the highly contagious bacterial respiratory illness. While typically milder in vaccinated adolescents and adults, pertussis can be life-threatening for infants and young children who are not fully immunized.