What is whooping cough (pertussis), its symptoms, diagnosis, treatment, and prevention in individuals of all ages?

Whooping Cough (Pertussis): Comprehensive Overview

What Is Pertussis?

Pertussis is a highly contagious acute respiratory infection caused by Bordetella pertussis, characterized by severe paroxysmal coughing that can affect individuals of all ages but poses the greatest risk to infants under 6 months. 1, 2

• The disease remains endemic worldwide despite widespread vaccination programs, with secondary attack rates exceeding 80% among susceptible household contacts. 1
• Transmission occurs through respiratory droplets, with infected individuals capable of spreading the disease to 70-100% of household contacts and 50-80% of school contacts. 3
• Adults and adolescents now serve as the primary reservoir and source of infection for vulnerable infants, as immunity from vaccination wanes 5-10 years after the last dose. 3, 1

Clinical Presentation

Three Distinct Disease Phases

Catarrhal Phase (1-2 weeks):

• Begins with insidious onset of nonspecific symptoms including nasal congestion, rhinorrhea, mild sore throat, conjunctivitis, malaise, and minimal or no fever. 3, 2
• The initially mild, intermittent cough gradually worsens during this highly contagious period. 2
• Leukocytosis and lymphocytosis, often considered typical of pertussis, are frequently absent. 3

Paroxysmal Phase (2-6 weeks):

• Characterized by severe coughing paroxysms consisting of a succession of expiratory bursts without inspiration, often followed by the classic high-pitched inspiratory "whoop." 3, 2
• Post-tussive vomiting is common across all age groups. 3, 2
• Coughing episodes increase in frequency and severity, occurring more frequently at night and after exposure to cold air. 3, 2
• The characteristic whooping sound is typically absent in adults and infants under 2 years of age. 3

Convalescent Phase (weeks to months):

• Gradual resolution of symptoms, though cough can persist for much longer than 6 weeks. 3

Age-Specific Presentations

Infants (<6 months):

• May present with atypical disease, initially showing apneic spells with minimal cough or other respiratory symptoms. 2
• Vomiting or apnea is more commonly seen than the typical whooping sound in children under 2 years. 3
• This age group has the highest risk for severe disease and death, with a case-fatality ratio of 1.8% among infants aged <2 months. 2

Adolescents and Adults:

• Often present with nondistinct protracted cough as the only manifestation, lacking the characteristic whoop. 3
• May complain of shortness of breath and tingling sensation in the throat. 3
• Many individuals never become symptomatic; clinical surveys show that only 37.5-50% of elderly subjects with serologic evidence of infection develop symptoms. 3

Vaccinated Children:

• Present with atypical symptoms, potentially lacking the characteristic "whoop" and experiencing less severe manifestations. 1
• Vaccination reduces disease duration and severity by approximately 50% compared to unvaccinated children. 1
• Median cough duration ranges from 29-39 days, with spasmodic cough lasting 14-29 days. 1

Diagnosis

Clinical Case Definitions

Probable Case:

• Acute illness with persistent cough >2 weeks associated with post-tussive vomiting, typical whooping sound, or severe paroxysms, without laboratory or epidemiologic confirmation. 3
• Pertussis should be suspected when cough lasts ≥2 weeks with paroxysms, post-tussive vomiting, and/or inspiratory whooping, even in fully vaccinated individuals. 1

Confirmed Case:

• Clinical case with isolation of B. pertussis or confirmation by PCR, or epidemiologic linkage to a confirmed case. 3

Diagnostic Testing

Nasopharyngeal Culture:

• Most reliable method for detection but requires enriched media. 3
• Sensitivity is low, reported as 25-50%, limiting its clinical utility. 3

PCR Testing:

• Recommended diagnostic modality alongside culture for confirmation. 1
• More sensitive than culture for detecting B. pertussis. 1

Serologic Testing:

• Not standardized or routinely recommended for diagnosis. 4

Common Diagnostic Pitfalls

• Do not dismiss pertussis based solely on vaccination status—breakthrough infections occur and should be actively considered. 1
• Do not assume typical "whooping" presentation—vaccinated children and adults often have atypical symptoms. 1
• Do not delay testing or treatment while waiting for classic symptoms to develop—early intervention reduces transmission and may shorten disease course. 1
• Many practitioners fail to consider pertussis in the differential diagnosis of chronic cough, despite it being confirmed in 19.9% of adolescents and adults with postinfectious cough. 3

Complications

Infants and Young Children

Respiratory Complications:

• Primary or secondary bacterial pneumonia occurs in approximately 13% of infants. 2
• Pneumothorax from severe coughing. 2
• Apneic episodes, particularly in infants under 6 months. 2

Neurologic Complications:

• Seizures and hypoxic encephalopathy are infrequent but serious complications requiring immediate evaluation. 1, 2

Other Complications:

• Substantial weight loss and feeding difficulties. 1, 2
• Sleep disturbance. 1, 2
• Epistaxis, subconjunctival hemorrhage, and subdural hematoma from pressure generated by severe coughing. 2
• Otitis media. 1

Adolescents and Adults

• Complications primarily result from chronic cough rather than severe respiratory disease. 4
• Pressure-related effects including pneumothorax, epistaxis, subconjunctival hemorrhage, and rib fracture. 1
• Only 1-2% of adolescents with confirmed pertussis require hospitalization. 1

Treatment

Antibiotic Therapy

First-Line Treatment:

Azithromycin is the preferred macrolide antibiotic for all age groups due to better tolerability, shorter treatment duration, and superior compliance compared to erythromycin. 1

• Dosing: 10 mg/kg (maximum 500 mg) on day 1, then 5 mg/kg (maximum 250 mg) daily for days 2-5. 1

Alternative Macrolides:

• Clarithromycin and erythromycin are acceptable alternatives with specific dosing regimens. 1
• Trimethoprim/sulfamethoxazole is an alternative in cases of macrolide allergy or intolerance. 4

Goals and Timing of Antibiotic Therapy

Primary Goal:

• The primary goal is to eradicate B. pertussis from the nasopharynx and reduce transmission, not to shorten disease duration in established cases. 1

Timing Considerations:

• Antibiotics administered early in the catarrhal stage can reduce symptom duration and severity by approximately 50%. 1
• Even when started during the paroxysmal stage, antibiotics remain critical for reducing transmission, as 80-90% of untreated patients spontaneously clear the organism within 3-4 weeks. 1
• Macrolide therapy eradicates B. pertussis from the nasopharynx regardless of when treatment begins. 1

Therapies to Avoid

Do not use β-agonists, antihistamines, corticosteroids, or pertussis immunoglobulin—these have no proven benefit in controlling coughing paroxysms or improving outcomes. 1

Contact Management

All household and close contacts require macrolide antibiotic prophylaxis for 14 days, regardless of age and vaccination status. 1

• Post-exposure prophylaxis should be administered within 21 days of exposure, particularly for household contacts and those at high risk of severe disease. 5
• Vaccinated individuals with breakthrough infections can still transmit disease to others, highlighting the importance of prophylaxis. 1

Infection Control Measures

Respiratory droplet precautions are required until 5 days of appropriate antibiotic treatment are completed. 1, 5

• If antibiotics cannot be administered, isolation should continue for 21 days after cough onset. 1
• Place confirmed pertussis patients in private rooms or cohort with other pertussis patients after the first 5 days of treatment. 1

Hospitalization Considerations

Infants Under 6 Weeks:

• Typically require hospital admission for 2-6 weeks, with duration depending on severity of symptoms and complications. 2
• Supportive care is the mainstay of management, including monitoring for apneic episodes, particularly at night when paroxysms may increase. 2

Risk Factors for Severe Disease Requiring Hospitalization:

• Age less than 6 months, with highest risk in those under 2 months. 2
• Unvaccinated or incompletely vaccinated status. 2
• Prematurity (gestational age <37 weeks). 2

Prevention

Vaccination Strategy

Vaccination is the most effective preventive strategy against pertussis. 2, 5

Pediatric Vaccination Schedule:

• DTaP vaccine is recommended at ages 2,4,6,15-18 months, and 4-6 years. 2
• Five doses of DTaP should be administered to children before 7 years of age. 4

Adolescent and Adult Vaccination:

• Tdap booster should be administered between 11 and 18 years of age. 4
• A single dose of Tdap booster is recommended for adults if not previously administered. 4

Vaccination Limitations and Considerations

• Neither vaccination nor natural disease provides lifelong protective immunity. 1
• Vaccination does not confer complete immunity—breakthrough infections occur due to waning immunity beginning 5-10 years post-vaccination. 1
• Primary vaccination is 80% effective, but protection is transient. 6
• Complete immunization is not protective for all children, and many children are incompletely immunized. 3

Post-Pertussis Vaccination:

• Children with well-documented pertussis should receive DT vaccine for remaining doses to ensure diphtheria and tetanus protection. 1
• No recommendation exists for administering additional pertussis vaccine doses to children with documented pertussis disease. 1
• Continue routine DTaP vaccination schedule for siblings and household contacts who are not up-to-date. 1

Current Epidemiological Trends

• Despite widespread vaccination, pertussis incidence has been increasing since the early 1980s across all age groups. 3
• The greatest increase has occurred in patients between 10 and 19 years of age, as immunity from immunization wanes in the decade following the most recent immunization. 3
• The annual incidence rate remains highest among infants <1 year of age, with adults serving as the source of infection in the majority of cases. 3
• Recent data from 2024 shows a sharp resurgence in countries like Brazil, with a 34.4-fold increase in cases compared to 2023, highlighting the ongoing public health challenge. 7