Pertussis

Definition/diagnostic criteria Pertussis, also known as whooping cough, is a highly contagious respiratory infection caused by the bacterium Bordetella pertussis. The condition is characterised by severe coughing spells, which may be accompanied by a ‘whooping’ sound upon inhalation. Diagnostic criteria include a history of prolonged coughing (usually lasting more than two weeks), paroxysms of coughing, inspiratory ‘whoop’ and post-tussive vomiting.

Epidemiology In the UK, pertussis is most prevalent in infants under 6 months of age, adolescents and adults, due to waning immunity. There is a cyclical pattern, with peaks in incidence every 3-4 years. The introduction of the pertussis vaccine has significantly reduced the incidence of the disease, particularly in vaccinated populations.

Diagnosis
Clinical features: Pertussis infection presents in stages. The catarrhal stage is characterised by mild respiratory symptoms resembling a common cold. This progresses to the paroxysmal stage marked by severe and prolonged coughing fits, followed by the convalescent stage where symptoms gradually subside. In infants, apnoea may be a significant feature.

Investigations: Laboratory confirmation can be obtained through culture of B. pertussis from a nasopharyngeal swab, although this has a limited window of sensitivity and is most reliable when conducted in the first two weeks of illness. Polymerase chain reaction (PCR) testing offers higher sensitivity. A full blood count may reveal lymphocytosis.

Treatment Antimicrobial therapy is recommended, particularly in the early stages of the disease or in severe cases. The antibiotic of choice is usually azithromycin. Supportive care is crucial, especially in infants and young children, and may include hospitalisation, oxygen therapy and close monitoring of respiratory status.

Offer antibiotic prophylaxis to close contacts when the symptoms in the index case occurred within the previous 21 days and the close contact is in a priority group (see NICE CKS for more details); offer immunisation to these groups too.

Prognosis The prognosis for pertussis is generally good, especially with early treatment and in individuals who have been vaccinated. However, complications can occur, particularly in unvaccinated infants, and may include pneumonia, seizures, encephalopathy and death. Long-term sequelae are rare but can include subdural haematoma and hernias due to the force of coughing.