Pertussis (Whooping Cough): Clinical Features, Epidemiology, and Preventive Strategies

Definition

• Pertussis is an acute bacterial infection of the respiratory tract caused by the gram‑negative bacillus Bordetella pertussis, transmitted via aerosolized respiratory droplets or direct contact with infected secretions. 1

Clinical Course

Catarrhal Phase (≈1–2 weeks)

• Infants and older children typically present with nasal congestion, rhinorrhea, mild sore throat, a dry cough, and little or no fever; these symptoms are indistinguishable from minor upper‑respiratory infections. 2, 3

Paroxysmal Phase (≈2–6 weeks)

• Cough becomes paroxysmal, ending with a characteristic inspiratory “whoop” and is often followed by post‑tussive vomiting. 1, 2

Convalescent Phase

• Symptoms resolve gradually; a non‑paroxysmal cough may persist for 2–6 weeks or longer. 4, 3

Atypical Presentation in Young Infants

• Infants may initially exhibit apnea episodes with minimal or absent cough and other respiratory signs. 2, 3

Risk in Unvaccinated/Partially Vaccinated Infants (<12 months)

• This age group has the highest risk of severe complications and death. 4

Epidemiology

Incubation Period

• The mean incubation period is 7–10 days (range 5–21 days). 2, 3

Period of Highest Infectivity

• Patients are most infectious during the catarrhal phase and the first three weeks after cough onset. 4

Secondary Attack Rate

• The secondary attack rate among susceptible contacts exceeds 80 %. 4

Vaccination (Primary Prevention)

General Principle

• Immunizing susceptible individuals is the most important preventive measure against pertussis. 4

Childhood Schedule (DTaP)

• Five doses are administered at ages 2 months, 4 months, 6 months, 15–18 months, and 4–6 years. 4

Current Coverage

• Childhood pertussis vaccination coverage remains historically high. 2

Adolescent Boosters (Tdap)

• A single reduced‑antigen Tdap dose is recommended for adolescents aged 11–18 years. 4

Adult Boosters (Tdap)

• A single Tdap dose is recommended for adults aged 19–64 years. 4

Duration of Immunity

• Neither vaccination nor natural infection confers lifelong immunity; protective immunity wanes 5–10 years after the last pertussis‑containing vaccine dose. 4

Post‑Exposure Antibiotic Prophylaxis

Preferred Agents

• Macrolide antibiotics—azithromycin, clarithromycin, or erythromycin—are the drugs of choice for post‑exposure prophylaxis. 1, 2, 3

Effect on Transmission

• Appropriate antibiotic therapy eradicates B. pertussis from the nasopharynx and shortens the period of infectivity. 4

Treatment and Infection‑Control Implications

Early Antibiotic Therapy

• Initiating antibiotics early can reduce the duration and severity of symptoms; when started after cough onset, it generally does not alter the clinical course but remains recommended to prevent onward transmission. 4

Maintaining High Vaccination Coverage

• Sustaining high pertussis vaccination rates among preschool children, adolescents, and adults is essential for community protection. 4

Protecting High‑Risk Populations

• Efforts should focus on minimizing exposure of infants and other high‑risk groups to pertussis sources. 4

Treatment and Management of Pneumonia and Pertussis

Clinical Presentation and Diagnosis

• Pneumonia presents with new lung infiltrates on imaging plus clinical evidence of infectious origin, including fever, abnormal white blood cell count, and purulent secretions, according to the American Thoracic Society 5
• Pertussis presents in three distinct phases: catarrhal, paroxysmal, and convalescent, as described by the Centers for Disease Control and Prevention 6

Treatment Approaches

• The American College of Chest Physicians recommends prompt empiric antibiotic therapy for pneumonia based on risk factors for specific pathogens and local resistance patterns 5
• The Centers for Disease Control and Prevention recommend macrolide antibiotics as the treatment of choice for pertussis, regardless of disease stage, with azithromycin as the preferred first-line option 7

Post-Exposure Prophylaxis

• The Centers for Disease Control and Prevention recommend post-exposure prophylaxis with macrolide antibiotics for close contacts of pertussis patients within 21 days of exposure, particularly for household contacts and those at high risk of severe disease 7

Infection Control Measures

• Standard precautions are recommended for hospital-acquired pneumonia, according to the American Thoracic Society 5
• Respiratory droplet precautions are recommended for pertussis patients until 5 days of appropriate antibiotic treatment are completed, as advised by the Centers for Disease Control and Prevention 8

Prevention

• Vaccination is the most effective preventive strategy for pertussis, with current recommendations including DTaP primary series for children and Tdap booster for adolescents and adults, according to the Centers for Disease Control and Prevention 8

Empiric Azithromycin Therapy for Suspected Pertussis

Clinical Diagnostic Criteria

• A cough persisting for more than two weeks that becomes paroxysmal and is accompanied by post‑tussive vomiting is a hallmark feature defining pertussis in adults. 9
• The typical physical examination in pertussis shows no fever, clear lung sounds, and a normal chest radiograph, making the exam often unremarkable between coughing episodes. 9

Guideline Recommendation for Diagnosis

• The American College of Chest Physicians states that when a cough is associated with paroxysms, post‑tussive vomiting, and/or an inspiratory “whoop,” the diagnosis of Bordetella pertussis should be made unless another cause is proven. 9

Treatment Recommendations

• Immediate initiation of macrolide therapy (azithromycin) is advised upon clinical suspicion of pertussis, without awaiting laboratory confirmation. 9
• Even when started after the catarrhal phase, azithromycin remains essential to eradicate B. pertussis from the nasopharynx and to prevent onward transmission to contacts. 9

Therapies Not Indicated for Pertussis

• Antihistamines have no role in the management of pertussis because the cough results from bacterial infection and airway inflammation, not histamine‑mediated mechanisms. 9
• Inhaled β‑agonists are not appropriate for active pertussis; while inhaled ipratropium may aid post‑infectious cough with airway hyperresponsiveness, antimicrobial therapy is required for pertussis infection. 9