Diagnosis of whooping cough (Pertussis)

​Clinical history of whooping cough

Table 1: Typical phases of whooping cough and associated clinical features

Phase Duration Clinical features Infectiousness
Incubation7-10 days
(range 5-21 days)		Asymptomatic (transmission is via inhalation of aerosolised droplets from an infectious case).Not infectious.
Catarrhal
(prodromal)		1-2 weeks
  • Rhinorrhoea.
  • Intermittent, dry, irritating cough.
  • Low-grade fever.
  • Symptoms often worse at night.
Infectious for first 3 weeks after onset or until after 5 days of antibiotic treatment (usually macrolides).
Paroxysmal1-6 weeksParoxysms of coughing.Infectious for first 3 weeks after onset or until after 5 days of antibiotic treatment (usually macrolides).
Convalescent1-6 weeks, sometimes longer.Cough gradually improves.Not infectious.
ImmuneA few yearsNo symptoms but immunity wanes after natural infection. Subsequent episodes may be milder. 

 

Notify the public health unit

Doctors must notify the public health unit once the diagnosis of whooping cough is suspected. 

Ring your public health unit.

Table 2: Clinical features of whooping cough vary with the patient's age

Age group Typical featuresComplications
Neonates and infants
  • Parents may complain their infant gags, gasps, chokes, turns blue or stops breathing.
  • Feeding difficulties are common.
  • Coughing paroxysms, post-tussive whoop or post-tussive vomiting are often absent.
  • Convalescent phase is often prolonged.
The youngest infants have the greatest incidence of complications from whooping cough which include:
  • apnoea
  • pneumonia
  • atelectasis
  • feeding problems & weight loss
  • hernias
  • hypoglycaemia
  • seizures
  • encephalopathy
  • sudden death.
Toddlers and older children
  • Prolonged paroxysms of coughing on a single breath.
  • Post-tussive whoop or post-tussive vomiting are common.
  • Prior to coughing paroxysms, the child may be relatively well.
  • During paroxysms, the child is extremely distressed and then is exhausted afterwards.
Complications are less frequent in older patients.
  • pneumonia
  • weight loss
  • syncope
  • rib fractures or strained chest wall muscles from severe coughing.
Teenagers and adults
  • A nonspecific protracted cough is common.
  • Only few have post-tussive whoop or post-tussive vomiting.
Complications are less frequent in older patients.
  • pneumonia
  • weight loss
  • syncope
  • rib fractures or strained chest wall muscles from severe coughing.

 

Don't dismiss whooping cough just because your patient is fully immunised

Vaccination is only 85% effective and immunity wanes after vaccination. Most cases in NSW are in people who have been vaccinated.

Physical examination

  • Mild fever is sometimes present.
  • There may be petechial haemorrhages on the upper body and subconjunctival haemorrhages.
  • Chest auscultation is often normal.

 

Don't wait for results of tests

If you suspect whooping cough on clinical grounds, ask the patient not to go near babies or pregnant women.

Differential diagnosis

Other infective causes of prolonged coughing illness include:

  • Bordetella parapertussis
  • Bordetella bronchiseptica
  • Mycoplasma pneumonia
  • Chlamydia pneumonia
  • Adenovirus
  • Respiratory syncytial virus

Current as at: Tuesday 18 October 2022
Contact page owner: Communicable Diseases