During which phase of pertussis is a patient most contagious?

During which phase of pertussis is a patient most contagious?

• A. Catarrhal phase
• B. Paroxysmal phase
• C. Convalescent phase
• D. Post-infectious phase

Answer: (A)

Contagiousness in pertussis is highest when the bacterial load in the nasopharynx is greatest, which occurs during the catarrhal phase. In this early stage, patients have mild upper-respiratory symptoms (like runny nose and low-grade fever) but carry a high amount of Bordetella pertussis and spread droplets readily. As the illness progresses to the paroxysmal phase, coughing fits dominate and bacterial shedding begins to decline, so contagiousness drops. In the convalescent and post-infectious phases, the bacterial burden is low and transmission is unlikely.

Contagiousness in pertussis is highest when the bacterial load in the nasopharynx is greatest, which occurs during the catarrhal phase. In this early stage, patients have mild upper-respiratory symptoms (like runny nose and low-grade fever) but carry a high amount of Bordetella pertussis and spread droplets readily. As the illness progresses to the paroxysmal phase, coughing fits dominate and bacterial shedding begins to decline, so contagiousness drops. In the convalescent and post-infectious phases, the bacterial burden is low and transmission is unlikely.