Pertussis (Whooping Cough) (Bordetella pertussis)
Overview
Plain-Language Overview
Pertussis (Whooping Cough) is a contagious respiratory infection caused by the bacterium Bordetella pertussis. It primarily affects the lungs and airways, leading to severe coughing spells that can make breathing difficult. The disease is known for its characteristic whooping sound during inhalation after coughing fits. It mainly impacts children, but can affect people of all ages. The infection spreads through airborne droplets when an infected person coughs or sneezes. Symptoms often start like a common cold but progress to intense coughing that can last for weeks. This condition can cause serious complications, especially in infants and those with weakened immune systems.
Clinical Definition
Pertussis (Whooping Cough) is an acute respiratory disease caused by the gram-negative coccobacillus Bordetella pertussis. The core pathology involves bacterial colonization of the ciliated respiratory epithelium, leading to the production of pertussis toxin and other virulence factors that disrupt normal mucociliary clearance and cause intense paroxysmal coughing. The disease progresses through three stages: catarrhal, paroxysmal, and convalescent. It is highly contagious and transmitted via respiratory droplets. The hallmark clinical feature is the paroxysmal cough followed by a characteristic inspiratory whoop, often accompanied by posttussive vomiting. Pertussis is a significant cause of morbidity and mortality in infants and unvaccinated populations worldwide. Diagnosis and early recognition are critical to prevent spread and complications such as pneumonia and apnea.
Inciting Event
Inhalation of aerosolized droplets containing Bordetella pertussis from an infected person initiates infection.
Close respiratory contact with symptomatic or asymptomatic carriers triggers transmission.
Exposure during outbreaks in community or institutional settings often precedes disease onset.
Lack of recent booster vaccination increases susceptibility to infection upon exposure.
Contact with contaminated respiratory secretions facilitates bacterial colonization.
Latency Period
Incubation period typically ranges from 7 to 10 days after exposure to Bordetella pertussis.
Symptoms usually begin within 5 to 21 days post-exposure, with variability based on host immunity.
Asymptomatic colonization can precede symptom onset by several days.
Early catarrhal phase symptoms appear around 1 to 2 weeks after infection.
Paroxysmal cough phase generally starts 1 to 2 weeks after initial symptoms.
Diagnostic Delay
Initial nonspecific symptoms resembling common cold lead to misdiagnosis or delayed suspicion.
Lack of awareness of pertussis in vaccinated adolescents and adults causes underdiagnosis.
Paroxysmal cough may be attributed to viral bronchitis or asthma, delaying testing.
Low sensitivity of culture and PCR if performed late in disease course reduces diagnostic yield.
Failure to obtain detailed exposure history or consider pertussis in differential diagnosis contributes to delay.
Clinical Presentation
Signs & Symptoms
Catarrhal phase with mild cough, rhinorrhea, and low-grade fever lasting 1-2 weeks
Paroxysmal phase characterized by intense coughing fits with inspiratory whoop and posttussive vomiting
Apnea especially in infants, can be a prominent symptom
Convalescent phase with gradual resolution of cough over weeks to months
Severe coughing spells often worsen at night and can cause exhaustion
History of Present Illness
Initial catarrhal phase with mild cough, rhinorrhea, and low-grade fever lasting 1 to 2 weeks precedes classic symptoms.
Paroxysmal phase characterized by sudden, severe coughing fits followed by inspiratory 'whoop' is hallmark.
Post-tussive vomiting and exhaustion commonly follow coughing paroxysms during the paroxysmal phase.
Coughing episodes worsen at night and may last 4 to 6 weeks or longer.
Convalescent phase involves gradual resolution of cough over weeks to months.
Past Medical History
Incomplete or absent pertussis vaccination history increases risk of infection.
History of chronic respiratory diseases such as asthma or bronchopulmonary dysplasia may worsen clinical course.
Previous pertussis infection may confer partial immunity but does not guarantee protection.
Immunodeficiency states can predispose to more severe or prolonged disease.
Recent exposure to individuals with respiratory infections or pertussis outbreaks is relevant.
Family History
No specific heritable syndromes are associated with pertussis susceptibility.
Family members often share exposure risk due to close contact and household transmission.
Clusters of pertussis cases within families are common during outbreaks.
Lack of vaccination in family members increases risk of spread to vulnerable individuals.
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Physical Exam Findings
Paroxysmal coughing fits often followed by a characteristic inspiratory whoop
Posttussive vomiting is frequently observed after severe coughing episodes
Cyanosis may be present during intense coughing spells, especially in infants
Tachypnea and signs of respiratory distress can be seen in severe cases
Conjunctival hemorrhages and petechiae may occur due to increased intrathoracic pressure during coughing
Diagnostic Workup
Diagnostic Criteria
Diagnosis of pertussis is established by a combination of clinical presentation and laboratory confirmation. The clinical criteria include a cough lasting at least 2 weeks with paroxysms of coughing, inspiratory whoop, or posttussive vomiting without other apparent cause. The gold standard diagnostic test is culture of Bordetella pertussis from nasopharyngeal swabs, although it has limited sensitivity. More sensitive and rapid confirmation is achieved by polymerase chain reaction (PCR) testing of nasopharyngeal specimens. Serologic testing may be used in later stages but is less specific. Early diagnosis relies heavily on clinical suspicion in the appropriate epidemiologic context.
Pathophysiology
Key Mechanisms
Adhesion of Bordetella pertussis to respiratory epithelium via filamentous hemagglutinin and pertactin initiates infection.
Production of pertussis toxin disrupts host immune response by ADP-ribosylation of G proteins, causing lymphocytosis and increased mucus production.
Tracheal cytotoxin damages ciliated respiratory epithelial cells, impairing mucociliary clearance and leading to cough.
Lymphocytosis-promoting factor causes marked peripheral lymphocytosis characteristic of the disease.
Local inflammation and increased mucus secretion contribute to airway obstruction and characteristic paroxysmal cough.
| Involvement | Details |
|---|---|
| Organs | Lungs are the primary site of infection and inflammation causing cough, hypoxia, and risk of pneumonia. |
Lymph nodes may be reactive due to immune activation and lymphocytosis induced by pertussis toxin. | |
| Tissues | Respiratory epithelium is damaged by bacterial toxins leading to characteristic paroxysmal cough and impaired mucociliary function. |
| Cells | Ciliated respiratory epithelial cells are the primary target of Bordetella pertussis toxins causing impaired mucociliary clearance. |
Lymphocytes increase markedly in peripheral blood due to pertussis toxin–induced lymphocytosis. | |
Macrophages participate in the immune response but are impaired by pertussis toxin, facilitating bacterial persistence. | |
| Chemical Mediators | Pertussis toxin disrupts G protein signaling leading to lymphocytosis and immune dysregulation. |
Adenylate cyclase toxin increases intracellular cAMP in immune cells, inhibiting phagocytosis. | |
Tracheal cytotoxin damages ciliated epithelial cells causing impaired clearance and cough. |
Treatments
Pharmacological Treatments
Macrolides (e.g., azithromycin, erythromycin)
- Mechanism:
Inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit of Bordetella pertussis.
- Side effects:
Gastrointestinal upset
QT prolongation
Hepatotoxicity
- Clinical role:
First-line
Trimethoprim-sulfamethoxazole
- Mechanism:
Inhibits folate synthesis in Bordetella pertussis, impairing bacterial DNA replication.
- Side effects:
Hypersensitivity reactions
Bone marrow suppression
Hyperkalemia
- Clinical role:
Second-line
Non-pharmacological Treatments
Supportive care including hydration and oxygen supplementation for respiratory distress.
Isolation precautions to prevent transmission during the contagious catarrhal and early paroxysmal stages.
Close monitoring for apnea and secondary bacterial pneumonia in infants.
Prevention
Pharmacological Prevention
DTaP vaccine for infants and children provides active immunization against pertussis
Tdap booster vaccine recommended for adolescents and adults to maintain immunity
Macrolide antibiotics (e.g., azithromycin) given as post-exposure prophylaxis to close contacts
Erythromycin or clarithromycin as alternative prophylactic agents in macrolide-intolerant patients
Non-pharmacological Prevention
Isolation of infected individuals during contagious period to prevent spread
Good respiratory hygiene and handwashing to reduce transmission
Avoiding contact with infants and unvaccinated individuals during outbreaks
Screening and vaccinating pregnant women to provide passive immunity to newborns
Outcome & Complications
Complications
Hypoxia and respiratory failure from severe airway obstruction during coughing
Apnea and sudden infant death syndrome (SIDS) in young infants
Rib fractures due to violent coughing
Pulmonary hypertension secondary to hypoxia
Seizures caused by hypoxia or intracranial hemorrhage
| Short-term Sequelae | Long-term Sequelae |
|---|---|
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Differential Diagnoses
Pertussis (Whooping Cough) (Bordetella pertussis) versus Viral Bronchiolitis
Pertussis (Whooping Cough) (Bordetella pertussis) | Viral Bronchiolitis |
|---|---|
Can affect all ages but more common in children under 10 years | Typically affects infants under 2 years old |
Characterized by paroxysmal coughing spells with inspiratory whoop lasting several weeks | Usually presents with wheezing and gradual improvement over 1-2 weeks |
Caused by the gram-negative bacterium Bordetella pertussis | Commonly caused by respiratory syncytial virus (RSV) |
Positive PCR or culture for Bordetella pertussis | Positive viral PCR or antigen test for RSV or other respiratory viruses |
Pertussis (Whooping Cough) (Bordetella pertussis) versus Asthma Exacerbation
Pertussis (Whooping Cough) (Bordetella pertussis) | Asthma Exacerbation |
|---|---|
Prolonged paroxysmal cough with characteristic inspiratory whoop | Episodic wheezing and dyspnea triggered by allergens or infections |
No specific eosinophilia; lymphocytosis may be present | Elevated eosinophils and IgE levels common |
Limited response to bronchodilators; macrolide antibiotics are effective | Rapid improvement with bronchodilators and corticosteroids |
Pertussis (Whooping Cough) (Bordetella pertussis) versus Chronic Cough due to Gastroesophageal Reflux Disease (GERD)
Pertussis (Whooping Cough) (Bordetella pertussis) | Chronic Cough due to Gastroesophageal Reflux Disease (GERD) |
|---|---|
Cough occurs in paroxysms often at night or after coughing fits | Chronic cough worsens with meals or lying down |
No typical GERD symptoms; history of exposure to infected individuals | History of heartburn or acid regurgitation |
Improves with macrolide antibiotics and supportive care | Improves with acid suppression therapy |
Pertussis (Whooping Cough) (Bordetella pertussis) versus Mycoplasma pneumoniae Infection
Pertussis (Whooping Cough) (Bordetella pertussis) | Mycoplasma pneumoniae Infection |
|---|---|
Caused by Bordetella pertussis | Caused by the atypical bacterium Mycoplasma pneumoniae |
Sudden onset of severe paroxysmal cough with inspiratory whoop | Gradual onset of dry cough with low-grade fever and malaise |
Positive PCR or culture for Bordetella pertussis | Positive cold agglutinin test or PCR for Mycoplasma pneumoniae |
Pertussis (Whooping Cough) (Bordetella pertussis) versus Tuberculosis (Pulmonary)
Pertussis (Whooping Cough) (Bordetella pertussis) | Tuberculosis (Pulmonary) |
|---|---|
Exposure to infected individuals with pertussis, often in household or community outbreaks | History of exposure to individuals with active tuberculosis or travel to endemic areas |
Paroxysmal nonproductive cough with inspiratory whoop, usually without systemic symptoms | Chronic productive cough with night sweats, weight loss, and hemoptysis |
Positive PCR or culture for Bordetella pertussis | Positive acid-fast bacilli smear or culture, or positive interferon-gamma release assay |