What symptom is most concerning in a case of suspected pertussis?

In a case of suspected pertussis, nocturnal coughing fits are the most concerning symptom because they are characteristic of the disease and indicate significant respiratory distress. Pertussis, commonly known as whooping cough, is marked by severe paroxysmal coughing that can lead to difficulty breathing, choking, and vomiting. The cough can often worsen at night, leading to fits that may last for minutes and can be exhausting for the patient.

These nocturnal coughing fits are part of the classic presentation of pertussis, making them a critical symptom to monitor in patients, especially in children who may be at higher risk for complications. Recognizing such symptoms allows for timely medical intervention, which is essential to manage the disease effectively and prevent transmission.