Clinical Features

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There are three stages to clinical course of pertussis:

  • Catarrhal
  • Paroxysmal
  • Convalescent

Pertussis symptoms usually develop within 5 to 10 days after exposure, but sometimes not for as long as 3 weeks. Pertussis has an insidious onset with catarrhal symptoms that are indistinguishable from those of minor respiratory tract infections. The cough, which is initially intermittent, can become paroxysmal. In typical cases, paroxysms terminate with “inspiratory whoop” and posttussive vomiting can follow. The illness can be milder and the characteristic paroxysmal cough and “whoop” may be absent in children, adolescents, and adults who were previously vaccinated.

Paroxysms of cough, which may occur more at night, usually increase in frequency and severity as the illness progresses. The cough typically persists for 1 to 6 weeks or more. After paroxysms subside, a nonparoxysmal cough can continue for 2 to 6 weeks or longer.

Unvaccinated or incompletely vaccinated infants younger than 12 months of age have the highest risk for severe complications and death. In infants, apnea may be the only symptom and the cough may be minimal or absent. There is increasing awareness and recognition of pertussis as a disease that affects adolescents and adults. However, clinicians often overlook pertussis in the differential diagnosis of cough illness in this population. Illness is generally less severe, and the typical “whoop” less frequently seen in adolescents and adults.

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It is important to educate parents to consider pertussis when their child has a cough. Let them know that it can be a severe illness, especially for infants, and they should seek immediate treatment.

Pediatric clinicians play a critical role in recognizing infant pertussis.

Infants may not have classic symptoms and only present with apnea.

Tips
  • Once you diagnose pertussis in a household, consider pertussis in coughing close contacts.
  • In the youngest infants, atypical presentation is common. The cough may be minimal or absent and the primary symptom can be apnea.
  • Remember, infants are at risk for severe or fatal pertussis. When you suspect a case in an older child, adolescent, or adult, inquire about contact with infants and pregnant women and consider prophylaxis.

Three stages to clinical course of pertussis, length, and clinical features
Stage Clinical Features
Stage 1: Catarrhal Characterized by:
  • Coryza
  • Low-grade fever
  • Mild, occasional cough (which gradually becomes more severe)
Stage 2: Paroxysmal* Characterized by:
  • Paroxysms of numerous, rapid coughs due to difficulty expelling thick mucus from the tracheobronchial tree
  • Long inspiratory effort accompanied by a high-pitched “whoop” at the end of the paroxysms
  • Cyanosis
  • Vomiting and exhaustion

Paroxysmal attacks:

  • Occur frequently at night, with an average of 15 attacks per 24 hours
  • Increase in frequency during the first 1-2 weeks, remain at the same frequency for 2-3 weeks, and then gradually decrease
Stage 3: Convalescent Characterized by:
  • Gradual recovery
  • Less persistent, paroxysmal coughs that disappear in 2-3 weeks

Paroxysms often recur with subsequent respiratory infections for many months after the onset of pertussis.

* Symptoms may be milder and paroxysmal cough may be absent, particularly in previously vaccinated individuals.

The timeline shows the typical clinical course of pertussis in weeks. The incubation period usually lasts from 5 to 10 days, but can last as long as 21 days. Following onset, the catarrhal stage can last anywhere from 1 to 2 weeks. During the late phase catarrhal stage a cough starts that becomes paroxysmal which marks the beginning of the paroxysmal stage that can last anywhere from 1 to 6 weeks. The paroxysmal stage is followed by the convalescent stage which can last from a week or two, to months in duration. The communicable period begins at symptom onset and lasts until 3 weeks after the paroxysmal cough begins.

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Page last reviewed: October 25, 2019
Content source: National Center for Immunization and Respiratory Diseases, Division of Bacterial Diseases