Evaluating and Managing Whooping Cough in Adults
Clinical Diagnosis
In adults with prolonged paroxysmal cough lasting more than 2 weeks, immediately assess for four key clinical features to diagnose pertussis: paroxysmal cough, posttussive vomiting, inspiratory whooping, and absence of fever. 1
Rule-Out Features (High Sensitivity)
- Absence of paroxysmal cough makes pertussis unlikely (sensitivity 93.2%, specificity 20.6%), meaning if the cough is not paroxysmal in nature, consider alternative diagnoses 1
- Presence of fever makes pertussis unlikely (sensitivity 81.8%, specificity 18.8%), as pertussis typically presents without fever 1
Rule-In Features (High Specificity)
- Posttussive vomiting strongly suggests pertussis when present (sensitivity 29.8%, specificity 79.5%), meaning few false-positives occur with this finding 1
- Inspiratory whooping strongly suggests pertussis when present (sensitivity 32.5%, specificity 77.7%), though this classic sign is frequently absent in previously vaccinated adults 1, 2
Key Definitions
- Paroxysmal cough: recurrent prolonged coughing episodes with multiple bursts of expiratory outflow and inability to breathe during spells 1
- Posttussive vomiting: vomiting directly induced by coughing episodes 1, 3
- Inspiratory whooping: continuous inspiratory airway sound with a whooping quality 1
Immediate Management
Start macrolide antibiotics immediately upon clinical suspicion without waiting for laboratory confirmation. 4, 2
Antibiotic Selection
- Azithromycin is the preferred agent due to better tolerability and compliance 4, 2
- Erythromycin is an effective alternative and eliminates the organism from the nasopharynx 4, 2
- Initiate treatment even if presenting beyond the catarrhal phase to prevent transmission to contacts, though clinical course may not be significantly altered if started late 4, 2
Infection Control
- Isolate patients for 5 days after starting antibiotic therapy to prevent transmission 4, 2
- Patients are most infectious during the first 3 weeks after cough onset 2, 5
- Identify and provide prophylaxis to close contacts, particularly infants, pregnant women in third trimester, and childcare workers 6
Laboratory Confirmation
Obtain nasopharyngeal specimens for PCR testing as the preferred confirmatory method, though treatment should never be delayed awaiting results 2, 7
- PCR testing is the most practical confirmatory test for pertussis 2, 7
- Culture is 100% specific but less sensitive and takes longer 2
- Serology showing fourfold increase in IgG or IgA antibodies to pertussis toxin has 72-100% specificity 2
Critical Pitfalls to Avoid
- Do not dismiss pertussis in vaccinated adults, as the illness can be milder with absent whoop in previously immunized individuals 2
- Do not rely on physical examination between coughing episodes, as the exam is often surprisingly unremarkable and normal lung auscultation is common 2
- Do not wait for leukocytosis with lymphocytosis, as this classic finding is frequently absent in adults and should not be relied upon for diagnosis 2
- Do not assume mild symptoms exclude pertussis, as adults frequently present with atypical symptoms ranging from mild cough to severe persistent cough 8, 5, 7
Expected Clinical Course
- The paroxysmal phase typically lasts 4-6 weeks, followed by a convalescent phase of 2-6 weeks or longer 2
- Nonparoxysmal cough can persist for months even after the acute phase resolves 2
- Treatment beyond 3 weeks after cough onset may be offered but the patient is unlikely to respond clinically, though it still prevents transmission 2
Public Health Notification
Inform local public health departments of all suspected cases to facilitate contact tracing and outbreak control 6