Whooping cough (pertussis)

Whooping cough is a highly contagious bacterial infection of the lower respiratory tract, of prolonged duration, due to Bordetella pertussis.
B. pertussis is transmitted through inhalation of droplets spread by infected individuals (coughing, sneezing).
The majority of cases arise in non-vaccinated or incompletely vaccinated individuals. Whooping cough affects all age groups. Signs and symptoms are usually minor in adolescents and adults. As a result the infection may be ignored, thus contributing to the spread of B. pertussis and infection in infants and young children, in whom the illness is severe.

Clinical features

After an incubation period of 7 to 10 days, the illness evolves in 3 phases:

• Catarrhal phase (1 to 2 weeks): coryza and cough. At this stage, the illness is indistinguishable from a minor upper respiratory infection.

• Paroxysmal phase (1 to 6 weeks):
  • Typical presentation: cough of at least 2 weeks duration, occurring in characteristic bouts (paroxysms), followed by a laboured inspiration causing a distinctive sound (whoop), or vomiting. Fever is absent or moderate, and the clinical exam is normal between coughing bouts; however, the patient becomes more and more fatigued.
  • Atypical presentations:
    • Infants under 6 months: paroxysms are poorly tolerated, with apnoea, cyanosis; coughing bouts and whoop may be absent.
    • Adults: prolonged cough, often without other symptoms.
  • Complications:
    • Major: in infants, secondary bacterial pneumonia (new-onset fever is an indicator); malnutrition and dehydration triggered by poor feeding due to cough and vomiting; rarely, seizures, encephalopathy; sudden death.
    • Minor: subconjunctival haemorrhage, petechiae, hernias, rectal prolapse.

• Convalescent phase: symptoms gradually resolve over weeks or months.

Management and treatment

Suspect cases

• Routinely hospitalise infants less than 3 months, as well as children with severe cases. Infants under 3 months must be monitored 24 hours per day due to the risk of apnoea.

• When children are treated as outpatients, educate the parents about signs that should lead to re-consultation (fever, deterioration in general condition, dehydration, malutrition, apnoea, cyanosis).

• Respiratory isolation (until the patient has received 5 days of antibiotic treatment):
  • at home: avoid contact with non-vaccinated or incompletely vaccinated infants;
  • in congregate settings: exclusion of suspect cases;
  • in hospital: single room or grouping together of cases away from other patients (cohorting).

• Hydration and nutrition: ensure children < 5 years are well hydrated; breastfeeding should continue. Advise mothers to feed the child frequently in small quantities after coughing bouts and the vomiting which follows. Monitor the weight of the child during the course of the illness, and consider food supplements for several weeks after recovery.

• Antibiotherapy:

Antibiotic treatment is indicated in the first 3 weeks after onset of cough. Infectivity is virtually nil after 5 days of antibiotherapy.

• For hospitalised children:
  • Place the child in a semi-reclining position (± 30°).
  • Oro-pharyngeal suction if needed.

Post-exposure prophylaxis

• Antibiotic prophylaxis (same treatment as for suspect cases) is recommended for unvaccinated or incompletely vaccinated infants of less than 6 months, who have had contact with a suspect case.

• Isolation of contacts is not necessary.

Note: pertussis vaccination should be updated in all cases (suspects and contacts). If the primary series has been interrupted, it should be completed, rather than restarted from the beginning.

Prevention

Routine vaccination with polyvalent vaccines containing pertussis antigens (e.g. DTP, or DTP + Hep B, or DTP + Hib + Hep B) from the age of 6 weeks or according to national protocol.
Neither vaccination nor natural disease confers lasting immunity. Booster doses are necessary to reinforce immunity and reduce the risk of developing disease and transmitting it to young children.