Pertussis (whooping cough)

Overview

Pertussis is a toxin-mediated infection of the respiratory tract caused by B. pertussis. The bacteria attach to ciliated airway cells and disrupt normal mucociliary clearance, producing a cough that can persist for many weeks even after the organism has been cleared. ^{[1] [2]}

The illness evolves in stages. During the early catarrhal stage, symptoms resemble a common cold and bacterial load is high. The paroxysmal stage brings bursts of rapid coughs, post-tussive vomiting and sometimes an inspiratory whoop. The convalescent stage is a slow decline in cough frequency and severity. ^{[1] [2]}

Vaccinated people can still develop pertussis because immunity wanes, but disease is often less severe. Infants—especially those too young to have completed primary vaccination—have the highest complication risk, which is why vaccination during every pregnancy and rapid household response are central prevention strategies. ^{[1] [2] [3]}

Symptoms and warning signs

Early symptoms include runny nose, nasal congestion, mild cough and low-grade fever. One to two weeks later, repeated coughing fits may cause vomiting, exhaustion or a whooping sound. Adults and adolescents may have only a prolonged severe cough, while young infants may have apnea, cyanosis or feeding difficulty with little obvious cough. ^{[1] [2]}

Call emergency services for an infant with apnea, blue color, severe breathing difficulty, poor responsiveness or repeated episodes of choking during cough. Any young infant with suspected pertussis deserves prompt medical assessment because deterioration can be rapid. ^{[1] [2]}

Diagnosis

Clinicians suspect pertussis from the duration and pattern of cough, exposure history and age. A nasopharyngeal swab or aspirate is collected because throat or anterior-nasal specimens are less suitable. PCR provides rapid sensitive detection, while culture is slower but highly specific and useful for surveillance. ^{[1] [2]}

Timing matters. Culture performs best early in illness, while PCR remains useful for several weeks after cough onset but can become less informative late in the course or after prolonged antibiotics. Serology may be used in selected later presentations depending on local laboratory practice. ^{[1] [2] [3]}

Viral respiratory infections, Mycoplasma infection, asthma, reflux and other causes of prolonged cough can mimic pertussis. In infants, bronchiolitis and other infections can cause apnea. A normal chest examination does not exclude pertussis because the main pathology is often in the airways rather than lung parenchyma. ^{[2] [3]}

Causes, risk factors and clinical context

Anyone without adequate immunity can be infected, but severe disease is concentrated in young infants. Household exposure, pregnancy, healthcare or childcare settings and close contact with a newborn increase the public-health importance of a case. ^{[1] [2]}

Cough can persist for weeks to months as damaged airway epithelium recovers. Paroxysms may recur temporarily with later respiratory infections. Antibiotics started after several weeks generally do not shorten established cough because bacterial toxins have already triggered airway injury. ^{[1] [2] [3]}

Complications and why the diagnosis matters

Infants can develop pneumonia, apnea, seizures, encephalopathy, dehydration and weight loss. Older children and adults may develop rib fractures, syncope, urinary leakage or hernias from forceful coughing, although life-threatening complications are much less common than in infants. ^{[1] [2]}

Most older children and adults recover fully, although the cough can be prolonged. Prognosis is more guarded in very young infants and in people with severe respiratory compromise; early recognition and supportive hospital care substantially reduce risk. ^{[1] [2] [3]}

Treatment and management

Macrolide antibiotics—commonly azithromycin, clarithromycin or erythromycin—are recommended for treatment, with trimethoprim-sulfamethoxazole as an alternative in selected older patients. Treatment during the first one to two weeks is most likely to lessen symptoms and also reduces transmission. ^{[1] [2]}

Infants may need hospital monitoring, oxygen, suctioning, feeding support and management of apnea. Cough suppressants generally have limited benefit. Hydration and avoidance of smoke or other airway irritants are practical supportive measures during the long convalescent period. ^{[1] [2] [3]}

Antibiotic selection depends on age, pregnancy, interactions and regional resistance. Very young infants require special prescribing considerations. Starting antibiotics late may still be appropriate for transmission control in selected patients, but families should understand that cough may persist despite successful bacterial eradication. ^{[1] [2]}

Follow-up, recovery and prevention

Persistent cough does not necessarily mean treatment failed. Follow-up focuses on breathing, feeding, weight, return to activity and complications. Infants and pregnant patients require closer follow-up, while public-health teams may monitor contacts and outbreak settings. ^{[1] [2]}

Routine DTaP and Tdap vaccination is the foundation of prevention. Tdap during each pregnancy provides transplacental antibodies to newborns. Respiratory hygiene, isolation during the infectious period and appropriate postexposure prophylaxis further reduce spread. ^{[1] [2] [3]}

Special situations and care pathway

Pregnant people in the third trimester and households with young infants receive special consideration because the main goal of PEP is preventing severe infant disease. Macrolide-resistant B. pertussis is uncommon in many settings but travel history can affect antibiotic choice. ^{[1] [2] [3]}

The pathway is clinical recognition, age/risk assessment, nasopharyngeal testing, prompt treatment when indicated, evaluation of close contacts and vaccination status, and supportive care through a prolonged cough recovery. ^{[1] [2]}

When to seek urgent medical care

Emergency assessment is needed for apnea, cyanosis, severe breathing difficulty, dehydration, seizure, markedly reduced responsiveness or a young infant with repeated coughing/choking spells. ^{[1] [2]}

Sources

1. CDC — Clinical Overview of Pertussis
2. CDC — Treatment of Pertussis
3. CDC — Pertussis Vaccination Recommendations

This article is based on trusted medical sources and is awaiting clinician review. It is not a substitute for personalized medical advice.