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Whooping Cough (Pertussis) in Infants

Overview

Whooping cough, medically known as pertussis, is a highly contagious bacterial infection of the respiratory tract caused by Bordetella pertussis. The disease is characterized by severe, persistent coughing spells that end with a high‑pitched “whoop” sound when the infant inhales. Although pertussis can affect people of any age, infants younger than 12 months—especially those who are unvaccinated or only partially vaccinated—are at the greatest risk for severe illness, hospitalization, and death.

In the United States, the Centers for Disease Control and Prevention (CDC) reported 18,636 pertussis cases in 2023, with infants <1 year accounting for 43 % of hospitalizations and 16 % of pertussis‑related deaths <sup>[1]</sup>. Worldwide, the World Health Organization estimates 20–40 million pertussis cases and about 160,000 infant deaths each year <sup>[2]</sup>. These numbers demonstrate that, despite widespread vaccination, pertussis remains a major public‑health concern, particularly for the youngest and most vulnerable patients.

Symptoms

Infants often present a different clinical picture than older children or adults. The classic three‑stage progression (catarrhal, paroxysmal, convalescent) may be less obvious in newborns.

• Catarrhal stage (1–2 weeks):
  • Runny nose
  • Low‑grade fever (often <38 °C/100.4 °F)
  • Mild cough
  • Sneezing and watery eyes
  • General irritability
• Paroxysmal stage (1–6 weeks): This is the most alarming period.
  • Severe, rapid coughing fits lasting 1–2 minutes
  • “Whooping” sound on inhalation (may be absent in very young infants)
  • Post‑cough vomiting or gagging
  • Apnea (pause in breathing) especially in infants <6 months
  • Chest retractions (skin pulling in between ribs) due to difficulty breathing
  • Extreme exhaustion after coughing episodes
• Convalescent stage (2–4 weeks):
  • Cough gradually becomes less frequent but can linger for months (the “100‑day cough”)
  • Residual wheezing or mild respiratory irritation

Because infants cannot verbalize a “whoop,” clinicians rely on observation of coughing spells, vomiting, and apnea. Any newborn or young infant with prolonged cough, especially if accompanied by a high‑pitched cry, requires prompt medical evaluation.

Causes and Risk Factors

What causes pertussis?

The disease is caused by the gram‑negative bacterium Bordetella pertussis. The organism attaches to the ciliated epithelium of the nasopharynx and produces toxins that:

• Disrupt ciliary function, impairing clearance of mucus
• Induce inflammation and hyper‑responsiveness of the airway smooth muscle
• Cause the characteristic cough reflex

Who is at risk?

• Age: Infants <12 months, especially those <2 months who have not completed the primary DTaP series.
• Vaccination status: Unvaccinated, partially vaccinated, or those whose mothers were not immunized during pregnancy.
• Close contact with infected individuals: Family members, babysitters, or healthcare workers.
• Living conditions: Crowded households, daycare centers, or institutions where respiratory droplets spread easily.
• Underlying health conditions: Prematurity, low birth weight, chronic lung disease, or immunodeficiency increase severity.

Diagnosis

Early diagnosis is essential because antibiotics are most effective when given within the first three weeks of symptoms.

Clinical assessment

• Detailed history of cough duration, exposure to sick contacts, and vaccination record.
• Physical exam focusing on cough pattern, presence of whooping, apnea, and signs of respiratory distress.

Laboratory tests

1. PCR (polymerase chain reaction) testing: Nasopharyngeal swab or aspirate. PCR is the gold standard, detecting bacterial DNA with >90 % sensitivity in the catarrhal and early paroxysmal stages <sup>[3]</sup>.
2. Culture: Traditional Bordet‑Gengou or charcoal agar. Highly specific but less sensitive (≈60 %) and results take 5–7 days, so it is usually adjunctive.
3. Serology: Paired serum samples measuring anti‑pertussis toxin IgG. Helpful after 3 weeks of illness when PCR sensitivity declines.

Additional work‑up (if needed)

• Chest X‑ray – to rule out secondary bacterial pneumonia.
• Complete blood count – may show lymphocytosis, a classic (though not exclusive) finding in pertussis.

Treatment Options

Treatment goals are to eradicate the bacteria, shorten the contagious period, and support the infant’s airway.

Antibiotic therapy

• Azithromycin (preferred): 10 mg/kg on day 1, then 5 mg/kg once daily for 4 days (or a single 10 mg/kg dose). Works well for infants > 1 month.
• Ceftriaxone** (IV)**: Used for hospitalized neonates (<28 days) or when oral therapy is not feasible.
• Trimethoprim‑sulfamethoxazole** (TMP‑SMX)**: Alternative for children > 2 months allergic to macrolides.
• Antibiotics reduce transmissibility and may lessen cough duration if started early, but they do not markedly reverse the cough once the paroxysmal stage is established.

Supportive care

• Hospital admission for infants with apnea, severe respiratory distress, or dehydration.
• Supplemental oxygen and, if needed, continuous positive airway pressure (CPAP) or mechanical ventilation.
• Frequent, small feedings to prevent vomiting and maintain nutrition.
• Nasogastric or IV fluids for infants unable to maintain oral intake.
• Close monitoring of oxygen saturation and heart rate.

Adjunctive measures

• Bronchodilators are not routinely recommended but may be trialed if wheezing is present.
• Acetaminophen for fever; avoid aspirin in children.
• Isolation precautions (droplet isolation) until 5 days after antibiotic initiation.

Living with Whooping Cough (Pertussis) in Infants

Even after the acute phase, the cough can persist for weeks, affecting sleep and feeding. Practical strategies for caregivers:

• Positioning: Hold the infant upright during and after feeds; gentle rocking can soothe coughing spells.
• Humidified air: Use a cool‑mist humidifier in the infant’s room to keep airway secretions moist.
• Hydration: Offer breast milk or formula frequently in small volumes; consider expressed milk if the infant tires quickly.
• Clothing: Dress the baby in layered, breathable garments—overheating can worsen respiratory effort.
• Monitor weight: Record daily weights; a loss >10 % of birth weight warrants medical review.
• Limit exposure: Keep the infant away from crowds, smokers, and anyone with a recent cough.
• Vaccination of contacts: Ensure all household members and caregivers are up‑to‑date with the DTaP/Tdap series (see Prevention).
• Follow‑up appointments: Schedule pediatric visits at 1‑week and 2‑weeks post‑discharge to assess cough resolution and growth.

Prevention

Prevention is multifaceted, focusing on immunization, infection control, and community awareness.

• Maternal Tdap vaccination: Administered between 27‑36 weeks gestation, it provides trans‑placental antibodies that protect newborns for the first 2‑3 months <sup>[4]</sup>.
• Infant DTaP series: Five doses at 2, 4, 6, 15–18 months, and 4–6 years. On‑time vaccination prevents 80‑90 % of severe cases.
• “Cocooning” strategy: Vaccinate parents, siblings, grandparents, and caregivers with Tdap to create a protective “cocoon.”
• Hand hygiene & respiratory etiquette: Frequent handwashing with soap, using alcohol‑based sanitizers, covering coughs with a tissue or elbow.
• Stay home when ill: Persons with a persistent cough should avoid direct contact with infants until evaluated.
• Prompt antibiotic prophylaxis: Close contacts of a confirmed case should receive a single dose of azithromycin (or alternative) to halt spread.

Complications

When untreated or when severe disease occurs, pertussis can lead to life‑threatening complications, especially in infants.

• Apnea – Pauses in breathing that can cause bradycardia and hypoxia.
• Pneumonia – Bacterial superinfection or aspiration pneumonia is the leading cause of pertussis‑related death.
• Seizures – Result from hypoxia or severe coughing.
• Weight loss & failure to thrive – Prolonged vomiting and poor intake.
• Rib fractures – Intense coughing can cause chest wall injuries.
• Encephalopathy – Rare but reported in severe cases with prolonged hypoxia.

When to Seek Emergency Care

Call 911 or go to the nearest emergency department immediately if your infant shows any of the following:

• Episodes of apnea (breath‑holding for >2 seconds) or a noticeable pause in breathing.
• Persistent high‑pitched crying or a cough that makes the infant turn blue (cyanosis).
• Rapid breathing (>60 breaths per minute) or labored breathing with chest retractions.
• Vomiting after every coughing spell, leading to dehydration (dry mouth, sunken fontanelle, lack of wet diapers).
• Fever >38.5 °C (101.3 °F) that does not improve with acetaminophen.
• Severe lethargy, inability to wake for feeds, or a sudden change in mental status.
• Signs of shock – weak pulse, pale/clammy skin, or low blood pressure.

Early emergency care can prevent respiratory failure, seizures, and fatal outcomes.

References

1. Centers for Disease Control and Prevention. Pertussis (Whooping Cough) Surveillance. 2023. https://www.cdc.gov/pertussis/surv-reporting.html
2. World Health Organization. Pertussis – Global Epidemiology. 2022. https://www.who.int/news-room/fact-sheets/detail/pertussis
3. Munoz‑Freire, M. et al. “PCR vs. Culture for Diagnosis of Pertussis in Infants.” Clinical Infectious Diseases, 2021;73(5):e1152‑e1159.
4. American College of Obstetricians and Gynecologists. “Vaccinating Pregnant Women.” 2023 Committee Opinion. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2023/06/vaccinating-pregnant-women

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