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I. DEFINITION

Pertussis (whooping cough) is a highly contagious respiratory tract infection caused by the gram-negative bacteria Bordetella pertussis. While children may present with the classic whooping cough, neonates often present with an atypical and severe disease course.

II. INCIDENCE

The Centers for Disease Control and Prevention (CDC) reported a national incidence rate of 6.5 cases per 100,000 in 2015, and despite vaccination, the incidence has been rising. The overall pertussis incidence rate among infants <12 months of age is approximately 118 per 100,000 person-years (infants <3 months of age have the highest incidence rate of ∼248 per 100,000 person-years). Outbreaks in neonatal units with serious morbidity have been reported.

III. PATHOPHYSIOLOGY

B pertussis is transmitted via close contact with respiratory secretions or aerosolized respiratory droplets. The source of pertussis infection in infants is unknown in about 50% of cases. In infants with a known origin of infection, the most commonly identified source has now shifted from mothers to siblings.

B pertussis is primarily a toxin-mediated disease. The organism produces multiple virulence factors including pertussis toxin, filamentous hemagglutinin, agglutinogens, adenylate cyclase, pertactin, and tracheal cytotoxin. Pertussis toxin leads to induction of lymphocytosis, and tracheal cytotoxin damages cilia in the respiratory epithelium via a nitric oxide synthase–dependent pathway. Lymphocytosis can lead to aggregation of leukocytes in the pulmonary circulation, causing severe pulmonary hypertension.

IV. RISK FACTORS

Infants <6 months of age are at highest risk for severe pertussis and complications or death from pertussis, especially if they are unvaccinated. Other risk factors include prematurity and low birthweight.

V. CLINICAL PRESENTATION

The 3 phases of classic pertussis, namely catarrhal (1–2 weeks), paroxysmal (2–6 weeks), and convalescent (2–6 weeks), are not typically observed in young infants. Neonatal cases tend to present with paroxysmal cough, gagging, bradycardia, gasping, apnea (67%), and cyanotic spells, but not fever or tachypnea. They do not have the characteristic “whoop” due to lack of prolonged inspiratory effort at the end of a paroxysm. Infants <6 months of age tend to have a short or absent catarrhal phase. The following complications may be observed in neonates and young infants with pertussis:

  1. Secondary infections. Pertussis can be complicated by secondary infections such as pneumonia (23%), meningoencephalitis, and otitis media.

  2. Ophthalmologic complications. The forceful coughing paroxysms characteristic of pertussis can result in eye bulging and subconjunctival, scleral, or rarely retinal hemorrhages.

  3. Central nervous system manifestations. Subdural bleeding may result from increased intracranial pressure secondary to the Valsalva effect of paroxysmal coughing. Seizures (2%) are attributed to hypoxemia from apnea or relentless coughing, but may also be due to hyponatremia secondary to pneumonia-induced syndrome of inappropriate antidiuretic hormone secretion. Encephalopathy (<0.5%) can also present with fever, convulsions, focal neurologic signs, and altered mental status.

  4. Respiratory complications. Infants with pertussis are at increased risk for severe pulmonary hypertension due to pulmonary vasoconstriction from hypoxia and acidosis secondary to recurrent prolonged apnea, as well as restriction of pulmonary blood flow from leukocyte aggregates. Neonates with pertussis have a greater need for mechanical ventilation due to frequent apnea, respiratory compromise during paroxysms of coughing, and pulmonary hypertension.

  5. Miscellaneous. The increased intrathoracic and intra-abdominal pressures associated with paroxysmal coughing can result in other physical sequelae such as epistaxis, petechiae, pneumothorax, and umbilical and inguinal hernias. Posttussive emesis can lead to alkalosis, dehydration, and malnutrition.

VI. DIAGNOSIS

Pertussis should be differentiated from other infectious ...

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