- Clinical science
Pertussis, or whooping cough, is a highly infectious disease of the respiratory tract caused by the gram-negative bacteria Bordetella pertussis. The disease is mainly transmitted via airborne droplets and is most commonly occurs in children. Typically, pertussis manifests in three stages, with the second and third stage characterized by an intense paroxysmal coughing that is followed by a distinctive whooping sound on inhalation and, in some cases, vomiting. Young infants may not develop the typical cough, and often present with apnea and cyanosis instead. The disease is most often diagnosed via laboratory tests, especially detection of B. pertussis in bacterial culture. However, as test results may take time to obtain, treatment should be initiated as soon as clinical suspicion of pertussis arises. Subsequent management includes hospitalization of high-risk patients (e.g., infants) and antibiotic therapy with macrolides. These may lessen the length and severity of the disease if administered early, while also reducing infectivity and further disease transmission. Macrolides are also the drug of choice for post-exposure prophylaxis (PEP), which is recommended for all people with a recent history of exposure to pertussis. PEP is administered regardless of the individual immunization status, as both vaccination and prior infection may shorten the disease course, but do not provide full immunity.
- Pathogen: Bordetella pertussis is a gram‑negative, obligate aerobic coccobacillus
- Transmission: airborne droplet (through coughing); direct contact with oral or nasal secretions
- Incubation period: on average 7–10 days
- Bordetella pertussis proliferates on ciliated epithelial cells of the respiratory mucosa → produces virulence factors → paralyze cilia of respiratory epithelium and cause inflammation → inflammatory exudate secreted into respiratory tract → compromises small airways → cough, pneumonia, cyanosis
- Bordetella pertussis produces pertussis toxin → catalyzes the ADP-ribosylation of the α subunit of Gi protein , thereby impairing it → adenylate cyclase activity is no longer inhibited by Gi protein → leads to accumulation of cAMP → impairs cell signaling pathways
- Neither vaccination nor actual infection confer lifelong or complete immunity.
Catarrhal stage (∼ 1–2 weeks)
- Nonspecific symptoms similar to an upper respiratory infection (mild cough, watery nasal discharge, rarely low-grade fever)
- Possibly conjunctivitis
Paroxysmal stage (∼ 2–6 weeks)
- Intense paroxysmal coughing (often occurring at night)
- Followed by the expulsion of phlegm or posttussive vomiting (risk of dehydration)
- In infants (< 6 months): risk of apnea; infants may not develop the typical cough and only manifest with apnea → close monitoring necessary!
Convalescent stage (weeks to months)
- Progressive reduction of symptoms
- Coughing attacks may persist over several weeks before resolving
A presumptive diagnosis of pertussis may be made based on clinical history and findings. However, if possible, laboratory tests should be performed to confirm the diagnosis.
- Clinical diagnosis possible in patients with a cough lasting ≥ 2 weeks and at least one of the following symptoms:
- Inquire about immunization history and possible contact with infectious persons.
- Blood count: lymphocyte-predominant leukocytosis (50,000–60,000/μL) that corresponds with disease severity
- Pathogen detection (to confirm the diagnosis)
- Early initiation of treatment, especially in high-risk patients (e.g., infants), while confirmatory laboratory tests are pending
- Hospitalization and monitoring: infants < 4 months; severe cases (e.g., respiratory distress, cyanosis, apnea, inability to feed)
- Oxygen administration with humidification
- Increased fluid intake and nutritional support
- If necessary, sedation
- Macrolides (e.g., azithromycin, clarithromycin, erythromycin)
- Early administration may lessen symptoms of the catarrhal stage and early paroxysmal stage.
- Late antibiotic administration has little influence on disease severity but reduces infectivity.
- In children > 3 months: very good; lengthy convalescence, but full recovery
- In children < 3 months: mortality 1–3%, particularly due to apnea
- Increased risk for complications: premature infants; children < 6 months; people with underlying cardiac, pulmonary, neurologic, or neuromuscular disease
- Routine immunization: administer DTaP vaccine (diphtheria, tetanus, and pertussis) at 2, 4, 6, and 15–18 months, as well as 4–6 years (see )
Booster vaccination: administer Tdap vaccine:
- Single dose at 7–10 years of age if immunization is incomplete;
- Single-dose boost at 11–18 years of age, at least 10 years following the last dose
- Contraindications: known anaphylactic reactions, encephalopathy following previous vaccination
Post-exposure prophylaxis: choice of antibiotics identical to treatment recommendations (see “Therapy” above)
- Household and close contacts of infected people; especially people at risk of developing complications or close contacts of high-risk individuals (see “Complications” above)
- Administered regardless of immunization status
- Isolation: for 5 days after initiation of antibiotic therapy
- Reporting: Pertussis is a notifiable disease