Overview
Highly contagious bacterial respiratory disease causing prolonged severe coughing fits with characteristic "whoop." Fatal in infants under 6 months. Prevented by DTP/Tdap vaccination.
Transmission
Overview
Highly contagious respiratory disease characterized by severe coughing fits.
Overview
Pertussis (whooping cough) is caused by Bordetella pertussis transmitted via respiratory droplets. Despite high childhood vaccination rates, pertussis remains one of the most common vaccine-preventable diseases globally, primarily due to waning immunity. Neonates and young infants face the highest risk of severe disease and death.
Emergency Signs
Seek emergency care immediately for infants and young children if:
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Blue lips or face (cyanosis) during coughing fits
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Apnea — periods of stopping breathing
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Inability to feed; weight loss
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Exhaustion after coughing paroxysms; limpness
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Seizures or loss of consciousness
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Rapid breathing between coughing episodes (may indicate pneumonia) For adults: prolonged cough >3 weeks with vomiting — test for pertussis even if vaccinated.
Detailed Symptoms
Most common signs and symptoms
Pertussis classically progresses through three stages:
Catarrhal stage (1–2 weeks): Resembles a mild cold — runny nose, sneezing, mild cough, low-grade fever. Highly contagious at this stage.
Paroxysmal stage (1–6 weeks):
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Sudden, severe coughing paroxysms — multiple rapid coughs in a single expiration
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"Whoop" — characteristic high-pitched inspiratory sound as patient gasps for air
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Posttussive vomiting
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Cyanosis during coughing fits (especially in infants)
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Apnea without coughing in infants <3 months (atypical presentation)
Convalescent stage (weeks to months): Gradual decrease in coughing frequency; residual cough may persist months ("100-day cough").
Knowing the symptoms is the first step to a quick response.
Course of Disease
Typical disease course:
- Incubation period: 7–10 days (range 5–21 days).
- Catarrhal stage (1–2 weeks): Mild cough, rhinorrhea, low-grade fever. Indistinguishable from common cold. Most infectious period.
- Paroxysmal stage (2–8 weeks): Characteristic paroxysms of rapid coughs followed by inspiratory "whoop" (more pronounced in children; often absent in adults and infants). Post-tussive vomiting. Paroxysms may be triggered by eating, drinking, or yawning. Between paroxysms, patient appears well.
- Convalescent stage (weeks to months): Gradual reduction in cough frequency and severity. Intercurrent respiratory infections may trigger temporary recurrence of paroxysmal coughing.
Atypical presentations: Adults and vaccinated children often have prolonged cough without classic whooping. Infants <3 months may present with apnea rather than cough.
Diagnosis
How this disease is identified
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Nasopharyngeal culture: gold standard
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most sensitive in catarrhal phase
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takes 5–7 days
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PCR (nasopharyngeal swab): most practical
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positive in paroxysmal stage
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detects bacterial DNA
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Serology (anti-PT IgG): useful in later stages (≥3 weeks after symptom onset)
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Clinical diagnosis: characteristic paroxysmal cough with whoop in an unvaccinated patient
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CBC: marked lymphocytosis (lymphocyte count >10,000/μL) is characteristic
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Report to public health authorities
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identify contacts for prophylaxis
Treatment
Available treatment methods
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Antibiotics (reduce transmission, not symptoms if started in paroxysmal stage):
- Azithromycin: 5-day course — drug of choice for infants and adults
- Clarithromycin: 7 days — alternative
- Trimethoprim-sulfamethoxazole: for patients unable to take macrolides
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Antibiotics are most effective in catarrhal phase — initiate promptly on clinical suspicion without waiting for culture
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Supportive care:
- Hospitalization for infants <6 months with apnea, poor feeding, or cyanosis
- Supplemental oxygen during severe paroxysms
- Small, frequent feeds; minimize stimuli that trigger coughing
- Avoid antitussives (ineffective and potentially harmful in infants)
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Chemoprophylaxis: azithromycin for all household contacts and high-risk close contacts regardless of age or vaccination status
Most cases are effectively treated with early diagnosis.
Prevention Details
How to protect yourself
DTP/Tdap vaccination is the cornerstone of pertussis prevention:
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Primary series: DTaP at 2, 4, 6 months
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boosters at 15–18 months and 4–6 years
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Adolescent/adult booster: Tdap (not Td) at 11–12 years
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single Tdap for adults who have not received it
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Maternal immunization: Tdap in each pregnancy (27–36 weeks) — most effective intervention to protect newborns before they can be vaccinated
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reduces infant pertussis by ~91%
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Cocooning strategy: vaccinate all household contacts and caregivers of newborns if not recently vaccinated with Tdap Immunity wanes after 5–10 years post-vaccination and 4–20 years post-natural infection.
Preparation is the best protection.
Travel Advice
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Ensure Tdap vaccination is current (within last 10 years) before travel with infants or to high-incidence regions.
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Traveling with newborns: ensure all household contacts are vaccinated (cocooning); defer non-essential travel with newborns to high-risk areas.
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Pertussis circulates globally — no truly low-risk destination for unvaccinated infants.
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Healthcare workers traveling abroad should receive Tdap if not recently vaccinated.
How common is it?
Statistics and geographic data
WHO estimates 24.1 million pertussis cases and 160,700 deaths annually worldwide (2018), mostly in infants. Despite >85% global vaccine coverage (3-dose primary series), pertussis remains endemic due to waning immunity, incomplete coverage in adults, and circulation in vaccinated individuals. Cyclical epidemics every 3–5 years persist in vaccinated populations. United States reported >48,000 cases in 2012 outbreak. Sub-Saharan Africa and South Asia carry the highest burden.
Risk Factors
Who is most at risk
Risk factors for pertussis infection and severe outcomes are primarily related to age, vaccination status, and proximity to infectious contacts.
Risk factors for infection:
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Waning immunity: Pertussis immunity is not lifelong, whether acquired through vaccination or natural infection. Acellular vaccine protection wanes after 4–6 years; whole-cell vaccine protection after 4–15 years; natural immunity after 7–20 years. This creates large pools of susceptible adolescents and adults who drive ongoing transmission.
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Household exposure: Secondary attack rates among susceptible household contacts are 80–90% — among the highest of any infectious disease. The primary source of infant infection is usually a household member (parent, sibling, or grandparent) with unrecognized pertussis.
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Incomplete vaccination: Children who have not completed the primary series (3 doses) have substantially higher risk. Even a partial series provides some protection, but full protection requires ≥3 doses.
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Crowded settings: Schools, daycare centers, military barracks, dormitories — pertussis outbreaks are frequently school-based.
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Epidemic cycles: Pertussis epidemics occur every 3–5 years even in countries with >90% DTP3 coverage, reflecting the accumulation of susceptible individuals as vaccine immunity wanes.
Risk factors for severe disease and death:
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Age <6 months: The highest-risk group for severe pertussis, hospitalization, and death. Infants this age have not yet completed the primary vaccine series and may lack protective maternal antibodies (especially if the mother was not vaccinated with Tdap during pregnancy). Apnea, pneumonia, pulmonary hypertension, and encephalopathy are disproportionately common.
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Prematurity and low birth weight: Increased risk of severe pertussis due to smaller airways, immature immune function, and lower transplacental antibody transfer.
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Absence of maternal Tdap vaccination: Infants born to unvaccinated mothers have 3–5× higher risk of pertussis in the first 2 months of life.
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Comorbid respiratory disease: Asthma, bronchopulmonary dysplasia, and other chronic lung conditions may exacerbate the severity and duration of pertussis.
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Extreme leukocytosis: WBC >100,000/µL in infants is an independent predictor of mortality, associated with leukostasis, pulmonary hypertension, and refractory hypoxemia.
Risk factors for prolonged cough in adults:
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Asthma and chronic respiratory conditions
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Active smoking
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Advanced age
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Immunocompromised status
Complications Details
Potential complications
Infants <6 months:
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Apnea (life-threatening; leading cause of death)
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Hypoxia and cyanosis during paroxysms
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Pneumonia (secondary bacterial infection — complicates ~25% of infant cases)
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Seizures from hypoxia/encephalopathy
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Pulmonary hypertension (severe, often fatal)
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ICU admission required in up to 25% of hospitalized infants
Older children and adults:
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Urinary incontinence from coughing pressure
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Rib fractures from severe cough
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Hernia, rectal prolapse
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Pneumothorax, epistaxis
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Syncope during paroxysms
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Encephalopathy (rare, possibly from hypoxia)
Recovery & Outlook
Expected outcomes and recovery
Infants <6 months: Highest morbidity and mortality. CFR 1–3% in unvaccinated infants. Leading cause of pertussis death.
Older children and adults: Rarely fatal but causes prolonged morbidity. "100-day cough."
Complications:
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Pneumonia (most common cause of death in infants): 5–10%.
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Seizures: 1–2%, usually febrile.
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Encephalopathy: 0.1–0.3%.
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Rib fractures, hernias, subconjunctival hemorrhage (from violent coughing).
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Post-pertussis cough hypersensitivity may persist for months.
Immunity: Natural infection confers 7–20 years of protection. Vaccine-induced immunity wanes over 5–10 years.