Pertussis is a prolonged infection of the upper respiratory tract caused by the bacterium Bordetella pertussis and characterized by paroxysms of an intense cough. Humans are the only known host.¹ Infection is spread by respiratory droplets, with an incubation period of 7 to 10 days.^1,2

Whooping cough

• Infection is characterized by three phases: Catarrhal, paroxysmal, and convalescent.^1,5,8
• Catarrhal phase: Usually begins with a 1- to 2-wk prodrome that resembles a common cold. This phase may be mild or absent in adolescents and adults given partial immunity from prior immunization. This is typically the most contagious phase.⁵
• After this initial phase, increased production of mucus occurs. Excessive lacrimation and conjunctival infection should heighten the suspicion for pertussis.
• Paroxysmal phase: Increased mucus production is followed by an intense, paroxysmal cough, typically 5 to 10 coughs during a single expiration, ending with gasps and an inspiratory whoop.¹ Whoop can be absent in infants <6 mo and in immunized patients.^5,8
• Cough tends to be more frequent at night.⁸
• In some children, apnea and cyanosis are noted; posttussive gagging and vomiting are characteristic of pertussis.^5,8 Fever is typically absent or minimal.
• Cases can be severe and life-threatening in young infants, particularly children <6 mo, and in rare cases has been associated with sudden death. Mortality is usually from prolonged paroxysms leading to frank exhaustion and apnea.
• The paroxysmal phase lasts from 2 wk to 2 mo.^1,8
• Convalescent phase: Lasts over 2 mo and is characterized by cough of decreasing severity. Other respiratory infections during this stage may lead to worsening of paroxysms.¹
• Complications include apnea, respiratory failure, secondary bacterial pneumonia (most common), anorexia, rectal prolapse, seizures, encephalopathy, periorbital edema, subconjunctival hemorrhage, petechiae, subcutaneous emphysema, pneumothorax, and pneumomediastinum.^8,9

Bordetella pertussis, a gram-negative rod that adheres to human cilia and respiratory epithelia²

• Croup
• Epiglottitis
• Foreign body aspiration
• Bacterial pneumonia
• Viral pneumonia
• Bronchiolitis
• Asthma exacerbation

• Thorough history and physical exam may provide a clinical diagnosis of pertussis. Providers should screen for specific symptoms in adults/adolescents: Paroxysmal cough, nighttime cough, posttussive vomiting, inspiratory whooping, and absence of fever.
• Culture of bacteria is the gold standard laboratory test and most specific.⁹ Culture should be from nasopharyngeal specimen by aspiration or by swabbing the posterior nasopharynx with a polyester-tipped, flocked-rayon, or calcium alginate swab.⁹ Highest isolation rate within the first 2 wk of infection. False negatives tend to present after first 2 wk of infection, in previously vaccinated patients, and in patients who have received antibiotics.⁹
• Polymerase chain reaction (PCR) is the most sensitive method for rapid detection of pertussis.⁹ PCR testing should be used only to confirm a diagnosis in persons with signs and symptoms consistent with pertussis. PCR testing sensitivity declines and is unlikely to be positive after 4 wk of infection.⁹ PCR testing after 5 days of treatment with antibiotics can cause false-negative results and is generally not recommended. PCR testing should be paired with culture for outbreak identification.^1,9
• Serologic tests for immunoglobulin G (IgG) can be considered 2 to 8 wk after symptom onset if other tests are negative/likely to be negative.⁹
• Chest x-ray if there is concern for concomitant pneumonia.

CBC, which usually demonstrates marked leukocytosis (as high as 60,000) and marked lymphocytosis¹⁰:

Up to 18,000 lymphocytes

• 70% to 80% of total WBCs are lymphocytes

Chest x-ray examination is of value if secondary bacterial pneumonia is suspected.

• Adequate hydration
• Control of secretions
• Maintenance of airway

Antibiotics (Table 1) are indicated:

• Azithromycin, clarithromycin, or erythromycin is recommended for child care workers in close contact with infected children and for all household contacts. Antimicrobial therapy should be given to all persons at high risk of severe disease from pertussis and who were in contact with a pertussis case within 21 days of cough onset: TMP/SMX can be given in two oral doses per day for those who do not tolerate macrolides.

• Hospitalization and observation for apnea in infants <4 mo should be considered with younger age, report of color change, and other interventions being predictors of complicated hospital course.^5,11

To intensive care setting for life-threatening infections:

• Pulmonologist
• Infectious disease specialist

Childhood and Adolescent Immunizations (Patient Information)

Pertussis (Patient Information)